vendredi 17 novembre 2017
NASA - Magnetospheric Multiscale Mission (MMS) patch.
Nov. 17, 2017
Interplanetary space is hardly tranquil. High-energy charged particles from the Sun, as well as from beyond our solar system, constantly whizz by. These can damage satellites and endanger astronaut health — though, luckily for life on Earth, the planet is blanketed by a protective magnetic bubble created by its magnetic field. This bubble, called the magnetosphere, deflects most of the harmful high-energy particles.
Nevertheless, some sneak through — and at the forefront of figuring out just how this happens is NASA’s Magnetospheric Multiscale mission, or MMS. New results show that tornado-like swirls of space plasma create a boundary tumultuous enough to let particles slip into near Earth space.
Animation above: This simulation of the boundary shows how areas of low density plasma, shown by blue, mix with areas of higher density plasma, red, forming turbulent tornadoes of plasma. Animation Credits: NASA/Takuma Nakamura.
MMS, launched in 2015, uses four identical spacecraft flying in a pyramid formation to take a three-dimensional look at the magnetic environment around Earth. The mission studies how particles transfer into the magnetosphere by focusing on the causes and effects of magnetic reconnection — an explosive event where magnetic field lines cross, launching electrons and ions from the solar wind into the magnetosphere.
By combining observations from MMS with new 3-D computer simulations, scientists have been able to investigate the small-scale physics of what’s happening at our magnetosphere’s borders for the first time. The results, recently published in a paper in Nature Communications, are key for understanding how the solar wind sometimes enters Earth’s magnetosphere, where it can interfere with satellites and GPS communications.
Inside the magnetosphere, the density of the space plasma — charged particles, like electrons and ions — is much lower than the plasma outside, where the solar wind prevails. The boundary, called the
magnetopause, becomes unstable when the two different density regions move at different rates. Giant swirls, called Kelvin Helmholtz waves, form along the edge like crashing ocean waves. The once-smooth boundary becomes tangled and squeezed, forming plasma tornadoes, which act as portholes for the transportation of charged particles from the solar wind into the magnetosphere.
Image above: Kelvin-Helmholtz waves, with their classic surfer's wave shape, are found in nature wherever two fluids meet, such as in these clouds. Image Credits: Danny Ratcliffe.
Kelvin Helmholtz waves are found across the universe wherever two materials of different density move past one another. They can be seen in cloud formations around Earth and have even been observed in other planetary atmospheres in our solar system.
Using large-scale computer simulations of this mixing, performed at the Oak Ridge National Laboratory in Oak Ridge, Tennessee, on the Titan supercomputer, and comparing them to observations MMS took while passing through such a region in space, scientists were able to show that the tornadoes were extremely efficient at transporting charged particles — much more so than previously thought. The comparisons between the simulations and observations allowed the scientists to measure the exact dimensions of the tornadoes. They found these tornadoes to be both large and small — ones reaching 9,300 miles spawned smaller tornadoes 60 to 90 miles wide and over 125 miles long.
MMS recently moved into a new orbit, flying on the far side of Earth, away from the Sun. Here too, it will continue to study magnetic reconnection, but focus instead on how energy and particles interact within Earth’s magnetosphere, in the long trailing magnetotail. Understanding such fundamental processes in Earth’s neighborhood helps improve our situational awareness of the space that surrounds us — crucial information as it becomes ever more filled with satellites and communications systems we depend on.
Learn more about the Magnetospheric Multiscale Mission: https://www.nasa.gov/mission_pages/mms/index.html
Learn more about NASA’s research on the Sun-Earth environment: https://www.nasa.gov/mission_pages/sunearth/index.html
Animation (mentioned9, Image (mentioned), Text, Credits: NASA/Rob Garner.
Publié par Orbiter.ch à 14:30
NASA - JUNO Mission logo.
Nov. 17, 2017
This color-enhanced image of a massive, raging storm in Jupiter’s northern hemisphere was captured by NASA’s Juno spacecraft during its ninth close flyby of the gas giant planet.
The image was taken on Oct. 24, 2017 at 10:32 a.m. PDT (1:32 p.m. EDT). At the time the image was taken, the spacecraft was about 6,281 miles (10,108 kilometers) from the tops of the clouds of Jupiter at a latitude of 41.84 degrees. The spatial scale in this image is 4.2 miles/pixel (6.7 kilometers/pixel).
The storm is rotating counter-clockwise with a wide range of cloud altitudes. The darker clouds are expected to be deeper in the atmosphere than the brightest clouds. Within some of the bright “arms” of this storm, smaller clouds and banks of clouds can be seen, some of which are casting shadows to the right side of this picture (sunlight is coming from the left). The bright clouds and their shadows range from approximately 4 to 8 miles (7 to 12 kilometers) in both widths and lengths. These appear similar to the small clouds in other bright regions Juno has detected and are expected to be updrafts of ammonia ice crystals possibly mixed with water ice.
Juno spacecraft orbiting Jupiter
Citizen scientists Gerald Eichstädt and Seán Doran processed this image using data from the JunoCam imager.
JunoCam's raw images are available for the public to peruse and process into image products at: http://www.missionjuno.swri.edu/junocam
More information about Juno is at:
https://www.nasa.gov/juno and http://missionjuno.swri.edu
Image, Animation, Text, Credits: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstädt/Seán Doran.
Publié par Orbiter.ch à 14:18
NASA - Hubble Space Telescope patch.
Nov. 17, 2017
This new picture of the week, taken by the NASA/ESA Hubble Space Telescope, shows the dwarf galaxy NGC 4625, located about 30 million light-years away in the constellation of Canes Venatici (The Hunting Dogs). The image, acquired with the Advanced Camera for Surveys (ACS), reveals the single major spiral arm of the galaxy, which gives it an asymmetric appearance. But why is there only one such spiral arm, when spiral galaxies normally have at least two?
Astronomers looked at NGC 4625 in different wavelengths in the hope of solving this cosmic mystery. Observations in the ultraviolet provided the first hint: in ultraviolet light the disk of the galaxy appears four times larger than on the image depicted here. An indication that there are a large number of very young and hot — hence mainly visible in the ultraviolet — stars forming in the outer regions of the galaxy. These young stars are only around one billion years old, about 10 times younger than the stars seen in the optical center. At first astronomers assumed that this high star formation rate was being triggered by the interaction with another, nearby dwarf galaxy called NGC 4618.
They speculated that NGC 4618 may be the culprit “harassing” NGC 4625, causing it to lose all but one spiral arm. In 2004 astronomers found proof for this claim. The gas in the outermost regions of the dwarf galaxy NGC 4618 has been strongly affected by NGC 4625.
Hubble Space Telescope (HST)
For images and more information about Hubble, visit:
Image, Animation, Text, Credits: ESA/Hubble & NASA/Text Credits: European Space Agency/NASA/Karl Hille.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 14:11
jeudi 16 novembre 2017
NASA - Spitzer Space Telescope patch.
November 16, 2017
Image above: The super-Earth exoplanet 55 Cancri e, depicted with its star in this artist's concept, likely has an atmosphere thicker than Earth's but with ingredients that could be similar to those of Earth's atmosphere. Image Credits: NASA/JPL.
Twice as big as Earth, the super-Earth 55 Cancri e was thought to have lava flows on its surface. The planet is so close to its star, the same side of the planet always faces the star, such that the planet has permanent day and night sides. Based on a 2016 study using data from NASA's Spitzer Space Telescope, scientists speculated that lava would flow freely in lakes on the starlit side and become hardened on the face of perpetual darkness. The lava on the dayside would reflect radiation from the star, contributing to the overall observed temperature of the planet.
Now, a deeper analysis of the same Spitzer data finds this planet likely has an atmosphere whose ingredients could be similar to those of Earth's atmosphere, but thicker. Lava lakes directly exposed to space without an atmosphere would create local hot spots of high temperatures, so they are not the best explanation for the Spitzer observations, scientists said.
"If there is lava on this planet, it would need to cover the entire surface," said Renyu Hu, astronomer at NASA's Jet Propulsion Laboratory, Pasadena, California, and co-author of a study published in The Astronomical Journal. "But the lava would be hidden from our view by the thick atmosphere."
Using an improved model of how energy would flow throughout the planet and radiate back into space, researchers find that the night side of the planet is not as cool as previously thought. The "cold" side is still quite toasty by Earthly standards, with an average of 2,400 to 2,600 degrees Fahrenheit (1,300 to 1,400 Celsius), and the hot side averages 4,200 degrees Fahrenheit (2,300 Celsius). The difference between the hot and cold sides would need to be more extreme if there were no atmosphere.
"Scientists have been debating whether this planet has an atmosphere like Earth and Venus, or just a rocky core and no atmosphere, like Mercury. The case for an atmosphere is now stronger than ever," Hu said.
Researchers say the atmosphere of this mysterious planet could contain nitrogen, water and even oxygen -- molecules found in our atmosphere, too -- but with much higher temperatures throughout. The density of the planet is also similar to Earth, suggesting that it, too, is rocky. The intense heat from the host star would be far too great to support life, however, and could not maintain liquid water.
Spitzer Space Telescope. Image Credits: NASA/JPL
Hu developed a method of studying exoplanet atmospheres and surfaces, and had previously only applied it to sizzling, giant gaseous planets called hot Jupiters. Isabel Angelo, first author of the study and a senior at the University of California, Berkeley, worked on the study as part of her internship at JPL and adapted Hu's model to 55 Cancri e.
In a seminar, she heard about 55 Cancri e as a potentially carbon-rich planet, so high in temperature and pressure that its interior could contain a large amount of diamond.
"It's an exoplanet whose nature is pretty contested, which I thought was exciting," Angelo said.
Spitzer observed 55 Cancri e between June 15 and July 15, 2013, using a camera specially designed for viewing infrared light, which is invisible to human eyes. Infrared light is an indicator of heat energy. By comparing changes in brightness Spitzer observed to the energy flow models, researchers realized an atmosphere with volatile materials could best explain the temperatures.
There are many open questions about 55 Cancri e, especially: Why has the atmosphere not been stripped away from the planet, given the perilous radiation environment of the star?
"Understanding this planet will help us address larger questions about the evolution of rocky planets," Hu said.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit:
Images (mentioned), Text, Credits: NASA/JPL/Elizabeth Landau.
Publié par Orbiter.ch à 18:37
ESA - Gaia Mission patch.
16 November 2017
It's the perfect meeting of old and new. Astronomers have combined the latest data from ESA's Gaia mission with a simple analysis technique from the 18th century to discover a massive star cluster that had previously escaped detection. Now, subsequent investigations are helping reveal the star-forming history of our Galaxy, the Milky Way.
Gaia: How to find a star cluster
Video above: Video explainer: How to find a star cluster. Video Credit: ESA.
In the latter years of the 18th century, astronomers William and Caroline Herschel began to count stars. William called the technique "star gauging" and his aim was to determine the shape of our Galaxy.
Ever since 1609, when Galileo lifted his telescope to the misty patch of light known as the Milky Way and saw that it was composed of myriad faint stars whose light all blurred together, we have known that there are different numbers of stars in different directions throughout space. This means that our local collection of stars, the Galaxy, must have a shape to it. Herschel set out to find out what that shape was.
He used a large telescope, twenty feet (610 cm) in length, mounted between tall wooden frames to sweep out a large circle in the sky that passed through the Milky Way at right angles. He then split this circle into more than 600 regions and counted or estimated the number of stars in each.
With this simple technique the Herschels produced the first shape estimate for the Galaxy. Fast-forward to the 21st century and now researchers use star counts to search for hidden star clusters and satellite galaxies. They look for regions where the density of stars rises higher than expected. These patches are called stellar over-densities.
Image above: Gaia's first sky map. Image Credits: ESA/Gaia/DPAC. Acknowledgement: A. Moitinho & M. Barros (CENTRA – University of Lisbon), on behalf of DPAC.
Back in 1785, Herschel's circular track passed close to the brightest star in the night sky Sirius. Now, scientists mining the first data released from the ESA spacecraft Gaia have revisited that particular area of the sky and made a remarkable discovery.
They have revealed a large star cluster that could have been discovered more than a century and a half ago had it not been so close to Sirius.
The cluster was spotted by Sergey E. Koposov, then at the University of Cambridge (UK) and now at Carnegie Mellon University Pennsylvania (USA), and his colleagues. They have been looking for star clusters and satellite galaxies in various surveys for the past decade. It was natural for them to do this with the Gaia mission's first data release.
Gaia is the European Space Agency's astrometric mission. Collecting positions, brightnesses and additional information for more than a billion sources of light, its data allows nothing less than the most precise 'star gauging' ever.
Gaia scanning the sky
Video above: Gaia scanning the sky. Video Credits: ESA/Gaia/DPAC. Acknowledgement: B. Holl (University of Geneva, Switzerland), A. Moitinho & M. Barros (CENTRA – University of Lisbon), on behalf of DPAC.
These days the laborious task of counting the stars is done by computers but the results still have to be scrutinised by humans. Koposov was combing the list of over-densities when he saw the massive cluster. At first it seemed too good to be true.
"I thought it must be an artefact related to Sirius," he says. Bright stars can create false signals, termed artefacts, that astronomers must be careful not to mistake for stars. An early paper from the Gaia team had even discussed artefacts around Sirius using a nearby patch of sky to the one Koposov was looking at.
Although he moved on and found another over-density that looked promising, his mind kept wanting to return to the first one. "I thought, 'That's strange, we shouldn't have that many artefacts from Sirius.' So I went and looked at it again. And I realised that it too was a genuine object," he says.
These two objects were named: Gaia 1 for the object located near Sirius, and Gaia 2, which is close to the plane of our Galaxy, and both were duly published. Gaia 1 in particular contains enough mass to make a few thousand stars like the Sun, is located 15 thousand light years away, and spread across 30 light years. This means it is a massive star cluster.
Image above: The brightest star in this WISE image is Sirius. To the left of Sirius, and centred on this image, is Gaia 1, a massive star cluster discovered by scientists mining Gaia data. Image Credits: Sergey Koposov; NASA/JPL; D. Lang, 2014; A.M. Meisner et al. 2017.
Collections of stars like Gaia 1 are called open clusters. They are families of stars that all form together and then gradually disperse around the Galaxy. Our own Sun very likely formed in an open cluster. Such assemblies can tell us about the star formation history of our Galaxy. Finding a new one that can be easily studied is already paying dividends.
"The age is of great interest," says Jeffrey Simpson, Australian Astronomical Observatory, who conducted follow-up observations with colleagues using the 4-metre-class Anglo-Australian telescope at Siding Springs Observatory, Australia.
Identifying 41 members of the cluster, Simpson and colleagues found that Gaia 1 is unusual in at least two ways. Firstly, it is about 3 billion years old. This is odd because there are not many clusters with this age in the Milky Way.
Typically clusters are either younger than a few hundred million years – these are the open clusters – or older than 10 billion years – these are a distinct class called globular clusters, which are found beyond the main bulk of stars in our Galaxy. Being of intermediate age, Gaia 1 might represent an important bridge in our understanding between the two populations.
Images above: Star cluster Westerlund 2. Image Credits: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team.
Images above: Globular cluster 47 Tucanae. Image Credits: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgment: J. Mack (STScI) and G. Piotto (University of Padova, Italy).
Secondly, its orbit through the galaxy is unusual. Most open clusters lie close to the plane of the Galaxy but Simpson found that Gaia 1 flies high above it before ducking down and passing underneath. "It might go as much as a kiloparsec (more than 3000 light years) above and below the plane," he says. About 90% of clusters never go more than a third of this distance.
Simulations of clusters with orbits like Gaia 1 find that they are stripped of stars and dispersed by these high velocity 'plane passages'. That puts it at odds with the age estimate.
"Our finding that Gaia 1 is three billion years old is curious as the models would have it not surviving anywhere near as long. More research is required to try and reconcile this," says Simpson.
To test a possible explanation, Alessio Mucciarelli, Universita' degli Studi di Bologna, Italy and colleagues investigated the chemical composition of Gaia 1. Such a study has the ability to see if the cluster formed outside of the Galaxy and has been caught in the act of falling in.
"The chemical composition of the stars can be considered a 'genetic' signature of their origin. If a stellar cluster formed in another galaxy, its chemical composition will be different with respect to that of our Galaxy," says Mucciarelli.
They found that the compositions were practically identical to those expected if Gaia 1 formed in the Milky Way – so the puzzle remains.
Now Mucciarelli hopes that the discrepancy might go away when Gaia releases more data. "Even if the orbital parameters seem to suggest a peculiar orbit, their uncertainties are large enough to prevent any firm conclusion. More accurate orbital parameters will be obtained with the second Gaia data release and we will better understand whether the orbit of Gaia 1 is peculiar or not," he says.
As well as finding new clusters, the Gaia data are proving useful for checking out the reality of previously reported associations of stars. "Using Gaia data I can see stars that share the same motion. So I can confirm which ones form real open clusters," says Andrés E. Piatti, Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.
He recently published a study that showed ten out of fifteen previously published open clusters were not really star clusters at all, they were just statistical flukes where a lot of unrelated stars happened to be passing in different directions through the same region of space.
It is laborious but vital work. "No one wants to spend their life doing this," says Piatti, "but it is necessary. If we can determine the real size of the cluster population we can learn a lot about the processes that the Galaxy has suffered during its lifetime."
In astronomy, the most famous list of star clusters, nebulae and galaxies was compiled by astronomer and comet hunter, Charles Messier, in the 18th century. Unaware of the importance of these objects, he designed his catalogue to stop the frustration felt by him and other astronomers in mistaking one of these 'deep-sky objects' for a nearby comet.
That original catalogue ran to 110 objects. If it hadn't been for the glare from Sirius obscuring the view, Gaia 1 would have been bright and obvious enough to have made it onto that list too. And there is every reason to think that there are more to come, thanks to Gaia.
The next data release will give accurate proper motions and distances to an unprecedented number of stars, which can be used to more efficiently find star clusters that were buried too deep in the stellar field or were too diffuse or too distant to be seen before.
There is always the possibility to find something totally new too. "I hope with the next data release we can find some new classes of objects too," says Simpson.
For the astronomers ready to explore the Gaia data, the adventure has only just begun. Gaia's second data release is scheduled for April 2018. Subsequent data releases are scheduled for 2020 and 2022.
A large pan-European team of expert scientists and software developers known as DPAC (Data Processing and Analysis Consortium), located in and funded by many ESA member states, is responsible for the processing and validation of Gaia's data with the final objective of producing the Gaia Catalogue.
"Gaia 1 and 2. A pair of new Galactic star clusters," by S. E. Koposov, V. Belokurov and G. Torrealba, is published in Monthly Notices of the Royal Astronomical Society, Volume 470, Issue 3, 21 September 2017, Pages 2702–2709, https://doi.org/10.1093/mnras/stx1182
"Siriusly, a newly identified intermediate-age Milky Way stellar cluster: A spectroscopic study of Gaia 1," by J. D. Simpson, G. M. De Silva, S. L. Martell, D. B. Zucker, A. M. N. Ferguson, E. J. Bernard, M. Irwin, J. Penarrubia and E. Tolstoy is accepted for publication in Monthly Notices of the Royal Astronomical Society, stx1892, https://doi.org/10.1093/mnras/stx1892
"Chemical composition of the stellar cluster Gaia1: no surprise behind Sirius," by A. Mucciarelli, L. Monaco, P. Bonifacio and I. Saviane, is published in Astronomy & Astrophysics, 603 (2017) L7, https://doi.org/10.1051/0004-6361/201731009
"On the physical reality of overlooked open clusters," by A. E. Piatti is published in Monthly Notices of the Royal Astronomical Society, Volume 466, Issue 4, 1 May 2017, Pages 4960–4973, https://doi.org/10.1093/mnras/stx081
First Gaia release (Gaia DR1): http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=58272
Second Gaia data release: https://www.cosmos.esa.int/web/gaia/release
Anglo-Australian telescope: https://www.aao.gov.au/about-us/AAT
ESA's Gaia mission: http://www.esa.int/Our_Activities/Space_Science/Gaia
Images (mentioned), Videos (mentioned), text, Credit: European Space Agency (ESA.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 18:22
ESA - Mars Express Mission patch.
16 November 2017
Sirenum Fossae perspective view
These striking features on Mars were caused by the planet’s crust stretching apart in response to ancient volcanic activity.
The fractures in the Sirenum Fossae region in the southern hemisphere were imaged by ESA’s Mars Express in March. They extend for thousands of kilometres in length, far beyond the boundaries of this image.
The fractures divide the crust into blocks: the movement along a pair of faults causes the centre section to drop down into ‘graben’ several kilometres wide and a few hundred metres deep. Elevated blocks of crust remain between the graben when there is a parallel series of fault, as seen in this scene.
Sirenum Fossae in context
The Sirenum Fossae are part of a larger radial fracture pattern around the Arsia Mons volcano in the Tharsis region, which is situated some 1800 km to the northeast.
Tharsis is the largest volcanic province on Mars, its far-reaching fracture system testament to the powerful influence this impressive volcanic province had on the planet.
Sirenum Fossae fractures
Indeed, the Sirenum Fossae fracture system seen here is thought to be associated with tectonic stresses arising from ancient volcanic activity in the Tharsis region. For example, the graben could either be caused by the planet’s crust stretching apart as a magma chamber bulges the crust above it, or alternatively as the crust collapsed along lines of weakness as the magma chamber emptied.
It is also possible that each graben was associated with an ancient volcanic dike: a steep corridor within the rock along which magma from the interior of Mars once propagated upwards, causing cracking along the surface.
Sirenum Fossae topography
In this case the graben could represent a giant ‘dike swarm’ extending from the volcanic centre. Dike swarms are also seen on Earth, as in Iceland where they are observed with surface fractures and graben sets in the Krafla fissure swarm.
As with any geological feature that cuts into the surface of the planet, the graben systems make for a good window into the subsurface. They also provide steep surfaces for active processes occurring in more recent times.
Sirenum Fossae in 3D
For example, NASA’s Mars Reconnaissance Orbiter identified gullies on some of the steep slopes in Sirenum Fossae, along troughs and in the rims of impact craters. What material carves out the small channels is a topic of active research: they were initially thought to be related to flowing water, but recent proposals suggest that seasonal frozen carbon dioxide – dry ice – flowing downslope may be responsible.
Mars Express: http://www.esa.int/Our_Activities/Space_Science/Mars_Express
Mars Express overview: http://www.esa.int/Our_Activities/Space_Science/Mars_Express_overview
Mars Express in-depth: http://sci.esa.int/marsexpress
ESA Planetary Science archive (PSA): http://www.rssd.esa.int/PSA
High Resolution Stereo Camera: http://berlinadmin.dlr.de/Missions/express/indexeng.shtml
HRSC data viewer: http://hrscview.fu-berlin.de/
Behind the lens... http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Behind_the_lens
Frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Frequently_asked_questions
Images, Text, Credits: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO/NASA MGS MOLA Science Team.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 17:55
Nov. 16, 2017
Life. It's the one thing that, so far, makes Earth unique among the thousands of other planets we've discovered. Since the fall of 1997, NASA satellites have continuously and globally observed all plant life at the surface of the land and ocean. During the week of Nov. 13-17, NASA is sharing stories and videos about how this view of life from space is furthering knowledge of our home planet and the search for life on other worlds.
As a young scientist, Tony del Genio of NASA's Goddard Institute for Space Studies in New York City met Clyde Tombaugh, the discoverer of Pluto.
The Living Planet
"I thought, 'Wow, this is a one-time opportunity,'" del Genio said. "I'll never meet anyone else who found a planet."
That prediction was spectacularly wrong. In 1992, two scientists discovered the first planet around another star, or exoplanet, and since then more people have found planets than throughout all of Earth's preceding history. As of this month, scientists have confirmed more than 3,500 exoplanets in more than 2,700 star systems. Del Genio has met many of these new planet finders.
How to Find a Living Planet
Video above: The more we see other planets, the more the question comes into focus: Maybe we're the weird one? Decades of observing Earth from space has informed our search for signs of habitability and life on exoplanets and even planets in our own solar system. We're taking a closer look at what we'ver learned about Earth - our only example of a planet with life - to our search for life the universe.
Del Genio is now co-lead of a NASA interdisciplinary initiative to search for life on other worlds. This new position as the lead of this project may seem odd to those who know him professionally. Why? He has dedicated decades to studying Earth, not searching for life elsewhere.
We know of only one living planet: our own. But we know it very well. As we move to the next stage in the search for alien life, the effort will require the expertise of planetary scientists, heliophysicists and astrophysicists. However, the knowledge and tools NASA has developed to study life on Earth will also be one of the greatest assets to the quest.
Image above: Left, an image of Earth from the DSCOVR-EPIC camera. Right, the same image degraded to a resolution of 3 x 3 pixels, similar to what researchers will see in future exoplanet observations. Image Credits: NOAA/NASA, Stephen Kane.
There are two main questions in the search for life: With so many places to look, how can we focus in on the places most likely to harbor life? What are the unmistakable signs of life -- even if it comes in a form we don't fully understand?
"Before we go looking for life, we're trying to figure out what kinds of planets could have a climate that's conducive to life," del Genio said. "We're using the same climate models that we use to project 21st century climate change on Earth to do simulations of specific exoplanets that have been discovered, and hypothetical ones."
Del Genio recognizes that life may well exist in forms and places so bizarre that it might be substantially different from Earth. But in this early phase of the search, "We have to go with the kind of life we know," he said.
Further, we should make sure we use the detailed knowledge of Earth. In particular, we should make sure of our discoveries on life in various environments on Earth, our knowledge of how our planet and its life have affected each other over Earth history, and our satellite observations of Earth’s climate.
Above all else, that means liquid water. Every cell we know of -- even bacteria around deep-sea vents that exist without sunlight -- requires water.
Life in the Ocean
Research scientist Morgan Cable of NASA's Jet Propulsion Laboratory in Pasadena, California, is looking within the solar system for locations that have the potential to support liquid water. Some of the icy moons around Saturn and Jupiter have oceans below the ice crust. These oceans were formed by tidal heating, that is, warming of the ice caused by friction between the surface ice and the core as a result of the gravitational interaction between the planet and the moon.
"We thought Enceladus was just boring and cold until the Cassini mission discovered a liquid water subsurface ocean," said Cable. The water is spraying into space, and the Cassini mission found hints in the chemical composition of the spray that the ocean chemistry is affected by interactions between heated water and rocks at the seafloor. The Galileo and Voyager missions provided evidence that Europa also has a liquid water ocean under an icy crust. Observations revealed a jumbled terrain that could be the result of ice melting and reforming.
As missions to these moons are being developed, scientists are using Earth as a testbed. Just as prototypes for NASA's Mars rovers made their trial runs on Earth's deserts, researchers are testing both hypotheses and technology on our oceans and extreme environments.
Cable gave the example of satellite observations of Arctic and Antarctic ice fields, which are informing the planning for a Europa mission. The Earth observations help researchers find ways to date the origin of jumbled ice. "When we visit Europa, we want to go to very young places, where material from that ocean is being expressed on the surface," she said. "Anywhere like that, the chances of finding evidence of life goes up -- if they're there."
Water in Space
For any star, it's possible to calculate the range of distances where orbiting planets could have liquid water on the surface. This is called the star's habitable zone.
Astronomers have already located some habitable-zone planets, and research scientist Andrew Rushby, of NASA Ames Research Center, in Moffett Field, California, is studying ways to refine the search. Location alone isn't enough. "An alien would spot three planets in our solar system in the habitable zone [Earth, Mars and Venus]," Rushby said, "but we know that 67 percent of those planets are not very habitable." He recently developed a simplified model of Earth's carbon cycle and combined it with other tools to study which planets in the habitable zone would be the best targets to look at for life, considering probable tectonic activity and water cycles. He found that larger rocky planets are more likely than smaller ones to have surface temperatures where liquid water could exist, given the same amount of light from the star.
Renyu Hu, of JPL, refined the search for habitable planets in a different way, looking for the signature of a rocky planet. Basic physics tells us that smaller planets must be rocky and larger ones gaseous, but for planets ranging from Earth-sized to about twice that radius, astronomers can't tell a large rocky planet from a small gaseous planet. Hu pioneered a method to detect surface minerals on bare-rock exoplanets and defined the atmospheric chemical signature of volcanic activity, which wouldn't occur on a gas planet.
When scientists are evaluating a possible habitable planet, "life has to be the hypothesis of last resort," Cable said. "You must eliminate all other explanations." Identifying possible false positives for the signal of life is an ongoing area of research in the exoplanet community. For example, the oxygen in Earth's atmosphere comes from living things, but oxygen can also be produced by inorganic chemical reactions.
Shawn Domagal-Goldman, of NASA's Goddard Space Flight Center in Greenbelt, Maryland, looks for unmistakable, chemical signs of life, or biosignatures. One biosignature may be finding two or more molecules in an atmosphere that shouldn't be there at the same time. He uses this analogy: If you walked into a college dorm room and found three students and a pizza, you could conclude that the pizza had recently arrived, because college students quickly consume pizza. Oxygen "consumes" methane by breaking it down in various chemical reactions. Without inputs of methane from life on Earth's surface, our atmosphere would become totally depleted of methane within a few decades.
Earth as Exoplanet
When humans start collecting direct images of exoplanets, even the closest one will appear as a handful of pixels in the detector – something like the famous "blue dot" image of Earth from Saturn. What can we learn about planetary life from a single dot?
Stephen Kane of the University of California, Riverside, has come up with a way to answer that question using NASA's Earth Polychromatic Imaging camera on the National Oceanic and Atmospheric Administration's Deep Space Climate Observatory (DSCOVR). These high-resolution images -- 2,000 x 2,000 pixels – document Earth's global weather patterns and other climate-related phenomena. "I'm taking these glorious pictures and collapsing them down to a single pixel or handful of pixels," Kane explained. He runs the light through a noise filter that attempts to simulate the interference expected from an exoplanet mission.
DSCOVR takes a picture every half hour, and it's been in orbit for two years. Its more than 30,000 images are by far the longest continuous record of Earth from space in existence. By observing how the brightness of Earth changes when mostly land is in view compared with mostly water, Kane has been able to reverse-engineer Earth's rotation rate -- something that has yet to be measured directly for exoplanets.
When Will We Find Life?
Every scientist involved in the search for life is convinced it's out there. Their opinions differ on when we'll find it.
"I think that in 20 years we will have found one candidate that might be it," says del Genio. Considering his experience with Tombaugh, he added, "But my track record for predicting the future is not so good."
Rushby, on the other hand, says, "It's been 20 years away for the last 50 years. I do think it's on the scale of decades. If I were a betting man, which I'm not, I'd go for Europa or Enceladus."
How soon we find a living exoplanet really depends on whether there's one relatively nearby, with the right orbit and size, and with biosignatures that we are able to recognize, Hu said. In other words, "There's always a factor of luck."
Images, Video, Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau/Alan Buis/Earth Science News Team, written by Carol Rasmussen.
Publié par Orbiter.ch à 08:13
mercredi 15 novembre 2017
ISS - Expedition 53 Mission patch.
Nov. 15, 2017
International Space Station (ISS). Animation Credit: NASA
The Expedition 53 astronauts are continuing to unload several thousand pounds of space cargo from the new Cygnus resupply ship that arrived Tuesday morning. Some of the new science cargo contains a bacteria that curiously loses its harmful properties in microgravity and CubeSats that will be deployed in Earth orbit.
The Cygnus is now installed on the Unity module and open for business. The astronauts entered the cargo craft Tuesday and started replenishing the station with almost 7,400 pounds of crew supplies, science experiments, spacewalk gear, station hardware and computer parts.
Image above: The Cygnus spacecraft is pictured after it had been grappled with the Canadarm2 robotic arm by astronauts Paolo Nespoli and Randy Bresnik on Nov. 14, 2017. Image Credit: NASA.
Some of the new research payloads will be looking at the space impacts on microbiology and botany. The advanced space research will explore the effectiveness of antibiotics on astronauts and observe how plants absorb nutrients in microgravity. Some pathogens for the STaARS Bioscience-5 study delivered aboard Cygnus have also been safely transferred to the NEXUS facility for later observation.
A couple of the newest technology experiments will deploy CubeSats to explore laser communications and hybrid solar panels. Scientists will study the ability of small satellites to communicate with each other using lasers and also explore if a combination of antenna and solar cells can speed up communication rates.
Expedition 53: https://www.nasa.gov/mission_pages/station/expeditions/expedition53/index.html
Effectiveness of antibiotics: https://www.nasa.gov/centers/ames/engineering/projects/ecamsat
Plants absorb nutrients in microgravity: https://www.nasa.gov/mission_pages/station/research/experiments/2717.html
STaARS Bioscience-5: https://www.nasa.gov/mission_pages/station/research/experiments/2644.html
Laser communications: https://www.nasa.gov/directorates/spacetech/small_spacecraft/ocsd_project.html
Hybrid solar panels: https://www.jpl.nasa.gov/cubesat/isara.php
Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html
International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html
Animation (mentioned), Image (mentioned), Text, Credits: NASA/Mark Garcia.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 17:03
NASA - Van Allen Probes Mission patch.
Nov. 15, 2017
Scientists have long known that solar-energized particles trapped around the planet are sometimes scattered into Earth’s upper atmosphere where they can contribute to beautiful auroral displays. Yet for decades, no one has known exactly what is responsible for hurling these energetic electrons on their way. Recently, two spacecraft found themselves at just the right places at the right time to witness first hand both the impulsive electron loss and its cause.
New research using data from NASA’s Van Allen Probes mission and FIREBIRD II CubeSat has shown that a common plasma wave in space is likely responsible for the impulsive loss of high-energy electrons into Earth’s atmosphere. Known as whistler mode chorus, these waves are created by fluctuating electric and magnetic fields. The waves have characteristic rising tones — reminiscent of the sounds of chirping birds — and are able to efficiently accelerate electrons. The results have been published in a paper in Geophysical Review Letters.
Van Allen Probes. Image Credit: NASA
Whistler waves as heard by the EMFISIS instrument aboard NASA’s Van Allen Probes as it passed around Earth. Credits: NASA/University of Iowa.
Download "Whistler Waves" (MP3): https://www.nasa.gov/specials/plasmawave/whistler.mp3
“Observing the detailed chain of events between chorus waves and electrons requires a conjunction between two or more satellites,” said Aaron Breneman, researcher at the University of Minnesota in Minneapolis, and lead author on the paper. “There are certain things you can’t learn by having only one satellite — you need simultaneous observations at different locations.”
The study combined data from FIREBIRD II, which cruises at a height of 310 miles above Earth, and from one of the two Van Allen Probes, which travel in a wide orbit high above the planet. From different vantage points, they could gain a better understanding of the chain of cause and effect of the loss of these high-energy electrons.
Image above: The Van Allen Belts, shown in green in this illustration, are concentric doughnut-shaped belts filled with charged particles, trapped by Earth’s magnetic field. Image Credits: Tony Phillips/NASA.
Far from being an empty void, the space around Earth is a jungle of invisible fields and tiny particles. It’s draped with twisted magnetic field lines and swooping electrons and ions. Dictating the movements of these particles, Earth’s magnetic environment traps electrons and ions in concentric belts encircling the planet. These belts, called the Van Allen Radiation Belts, keep most of the high-energy particles at bay.
Sometimes however, the particles escape, careening down into the atmosphere. Typically, there is a slow drizzle of escaping electrons, but occasionally impulsive bunches of particles, called microbursts, are scattered out of the belts.
Late on Jan. 20, 2016, the Van Allen Probes observed chorus waves from its lofty vantage point and immediately after, FIREBIRD II saw microbursts. The new results confirm that the chorus waves play an important role in controlling the loss of energetic electrons — one extra piece of the puzzle to understand how high-energy electrons are hurled so violently from the radiation belts. This information can additionally help further improve space weather predictions.
Geophysical Review Letters: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075001/epdf
Learn more about the Van Allen Probes: https://www.nasa.gov/van-allen-probes
Learn more about NASA’s research on the Sun-Earth System: https://www.nasa.gov/mission_pages/sunearth/index.html
Van Allen Probes: https://www.nasa.gov/mission_pages/rbsp/main/index.html
Images (mentioned), Text, Credits: NASA/Rob Garner/ Goddard Space Flight Center, by Mara Johnson-Groh.
Publié par Orbiter.ch à 16:49
CASC - China Aerospace Science and Technology Corporation logo.
Nov. 14, 2017
Image above: A Long March 4C rocket lifts off from the Taiyuan space center Tuesday with the Fengyun 3D weather satellite. Image Credit: Xinhua.
A Chinese Long March 4C rocket launched Tuesday with a new polar-orbiting weather observatory named Fengyun 3D, replacing an aging satellite for the China Meteorological Administration.
The Fengyun 3D satellite lifted off at 18:35 GMT (12:35 p.m. EST) Tuesday from the Taiyuan space center in Shanxi province located in northeastern China.
China Launches Fengyun-3D Meteorological Satellite
A three-stage Long March 4C rocket boosted the approximately 2.5-ton satellite toward the south from Taiyuan, where launch occurred at 2:35 a.m. local time Wednesday
The Long March 4C’s three liquid-fueled stages placed the Fengyun 3D satellite in a 500-mile-high (800-kilometer) polar orbit tilted 98.7 degrees to the equator, according to tracking data released by the U.S. military.
Fengyun 3D hosts 10 instruments to collect data on atmospheric conditions, cloud and storm movements, ozone health and greenhouse gases, the China Meteorological Administration said in a statement announcing the successful launch.
Artist's illustration of the Fengyun 3D satellite. Image Credit: CMA
The new satellite, designed for mission of eight years, “will help people learn about the future weather conditions earlier and reduce the economic and social impact of natural disasters,” CMA said in a statement. “Its ability to detect aerosols and greenhouse gases will play an active role in coping with climate change.”
Fengyun 3D will replace the Fengyun 3B weather satellite launched in November 2010. Another Chinese weather satellite already in orbit — Fengyun 3C — will conduct tandem observations with the newest member of the fleet.
Tuesday’s launch placed Fengyun 3D into an orbit that passes overhead in the afternoon. Fengyun 3C is in a mid-morning orbit, giving Chinese forecasters a snapshot of weather conditions twice a day.
For more information about China Aerospace Science and Technology Corporation (CASC), visit: http://english.spacechina.com/n16421/index.html
Images (mentioned), Video (CCTV+), Text, Credits: CASC/Spaceflight Now/Stephen Clark.
Publié par Orbiter.ch à 08:36
ESO - European Southern Observatory logo.
15 November 2017
ESO’s HARPS instrument finds Earth-mass exoplanet around Ross 128
Artist’s impression of the planet Ross 128 b
A temperate Earth-sized planet has been discovered only 11 light-years from the Solar System by a team using ESO’s unique planet-hunting HARPS instrument. The new world has the designation Ross 128 b and is now the second-closest temperate planet to be detected after Proxima b. It is also the closest planet to be discovered orbiting an inactive red dwarf star, which may increase the likelihood that this planet could potentially sustain life. Ross 128 b will be a prime target for ESO’s Extremely Large Telescope, which will be able to search for biomarkers in the planet's atmosphere.
A team working with ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile has found that the red dwarf star Ross 128 is orbited by a low-mass exoplanet every 9.9 days. This Earth-sized world is expected to be temperate, with a surface temperature that may also be close to that of the Earth. Ross 128 is the “quietest” nearby star to host such a temperate exoplanet.
The sky around the red dwarf star Ross 128
“This discovery is based on more than a decade of HARPS intensive monitoring together with state-of-the-art data reduction and analysis techniques. Only HARPS has demonstrated such a precision and it remains the best planet hunter of its kind, 15 years after it began operations,” explains Nicola Astudillo-Defru (Geneva Observatory – University of Geneva, Switzerland), who co-authored the discovery paper.
Red dwarfs are some of the coolest, faintest — and most common — stars in the Universe. This makes them very good targets in the search for exoplanets and so they are increasingly being studied. In fact, lead author Xavier Bonfils (Institut de Planétologie et d'Astrophysique de Grenoble – Université Grenoble-Alpes/CNRS, Grenoble, France), named their HARPS programme The shortcut to happiness, as it is easier to detect small cool siblings of Earth around these stars, than around stars more similar to the Sun .
The red dwarf star Ross 128 in the constellation of Virgo
Many red dwarf stars, including Proxima Centauri, are subject to flares that occasionally bathe their orbiting planets in deadly ultraviolet and X-ray radiation. However, it seems that Ross 128 is a much quieter star, and so its planets may be the closest known comfortable abode for possible life.
Although it is currently 11 light-years from Earth, Ross 128 is moving towards us and is expected to become our nearest stellar neighbour in just 79 000 years — a blink of the eye in cosmic terms. Ross 128 b will by then take the crown from Proxima b and become the closest exoplanet to Earth!
Zooming in on Ross 128
With the data from HARPS, the team found that Ross 128 b orbits 20 times closer than the Earth orbits the Sun. Despite this proximity, Ross 128 b receives only 1.38 times more irradiation than the Earth. As a result, Ross 128 b’s equilibrium temperature is estimated to lie between -60 and 20°C, thanks to the cool and faint nature of its small red dwarf host star, which has just over half the surface temperature of the Sun. While the scientists involved in this discovery consider Ross 128b to be a temperate planet, uncertainty remains as to whether the planet lies inside, outside, or on the cusp of the habitable zone, where liquid water may exist on a planet’s surface .
Astronomers are now detecting more and more temperate exoplanets, and the next stage will be to study their atmospheres, composition and chemistry in more detail. Vitally, the detection of biomarkers such as oxygen in the very closest exoplanet atmospheres will be a huge next step, which ESO’s Extremely Large Telescope (ELT) is in prime position to take .
Flying through the Ross 128 planetary system
“New facilities at ESO will first play a critical role in building the census of Earth-mass planets amenable to characterisation. In particular, NIRPS, the infrared arm of HARPS, will boost our efficiency in observing red dwarfs, which emit most of their radiation in the infrared. And then, the ELT will provide the opportunity to observe and characterise a large fraction of these planets,” concludes Xavier Bonfils.
 A planet orbiting close to a low-mass red dwarf star has a larger gravitational effect on the star than a similar planet orbiting further out from a more massive star like the Sun. As a result, this “reflex motion” velocity is much easier to spot. However, the fact that red dwarfs are fainter makes it harder to collect enough signal for the very precise measurements that are needed.
 The habitable zone is defined by the range of orbits around a star in which a planet can possess the appropriate temperature for liquid water to exist on the planet’s surface.
 This is only possible for the very few exoplanets that are close enough to the Earth to be angularly resolved from their stars.
This research was presented in a paper entitled “A temperate exo-Earth around a quiet M dwarf at 3.4 parsecs”, by X. Bonfils et al., to appear in the journal Astronomy & Astrophysics.
The team is composed of X. Bonfils (Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France [IPAG]), N. Astudillo-Defru (Observatoire de Genève, Université de Genève, Sauverny, Switzerland), R. Díaz (CONICET – Universidad de Buenos Aires, Instituto de Astronomía y Física del Espacio (IAFE), Buenos Aires, Argentina), J.-M. Almenara (Observatoire de Genève, Université de Genève, Sauverny, Switzerland), T. Forveille (IPAG), F. Bouchy (Observatoire de Genève, Université de Genève, Sauverny, Switzerland), X. Delfosse (IPAG), C. Lovis (Observatoire de Genève, Université de Genève, Sauverny, Switzerland), M. Mayor (Observatoire de Genève, Université de Genève, Sauverny, Switzerland), F. Murgas (Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain), F. Pepe (Observatoire de Genève, Université de Genève, Sauverny, Switzerland), N. C. Santos (Instituto de Astrofísica e Ciências do Espaço and Universidade do Porto, Portugal), D. Ségransan (Observatoire de Genève, Université de Genève, Sauverny, Switzerland), S. Udry (Observatoire de Genève, Université de Genève, Sauverny, Switzerland) and A. Wü̈nsche (IPAG)
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and by Australia as a strategic partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.
ESOcast 137 Light: Temperate Planet Orbiting Quiet Red Dwarf: http://www.eso.org/public/videos/eso1736a/
Research paper in Astronomy & Astrophysics: https://www.eso.org/public/archives/releases/sciencepapers/eso1736/eso1736a.pdf
Photos of the ESO 3.6-metre telescope: https://www.eso.org/public/images/archive/search/?adv=&subject_name=3.6
More information about HARPS: https://www.eso.org/public/teles-instr/lasilla/36/harps/
ESO’s High Accuracy Radial velocity Planet Searcher (HARPS): https://www.eso.org/public/teles-instr/lasilla/36/harps/
ESO’s Extremely Large Telescope (ELT): https://www.eso.org/elt/
Images, Text, Credits: ESO/Richard Hook/M. Kornmesser/Geneva Observatory – University of Geneva/Nicola Astudillo-Defru/Institut de Planétologie et d'Astrophysique de Grenoble – Université Grenoble-Alpes/CNRS/Xavier Bonfils/Digitized Sky Survey 2. Acknowledgement: Davide De Martin/IAU and Sky & Telescope/Videos: ESO/M. Kornmesser/Digitized Sky Survey 2/Nick Risinger (skysurvey.org).
Best regards, Orbiter.ch
Publié par Orbiter.ch à 05:42
mardi 14 novembre 2017
Nov. 14, 2017
Life. It's the one thing that, so far, makes Earth unique among the thousands of other planets we've discovered. Since the fall of 1997, NASA satellites have continuously and globally observed all plant life at the surface of the land and ocean. During the week of Nov. 13-17, NASA is sharing stories and videos about how this view of life from space is furthering knowledge of our home planet and the search for life on other worlds.
NASA satellites can see our living Earth breathe.
In the Northern Hemisphere, ecosystems wake up in the spring, taking in carbon dioxide and exhaling oxygen as they sprout leaves — and a fleet of Earth-observing satellites tracks the spread of the newly green vegetation.
Meanwhile, in the oceans, microscopic plants drift through the sunlit surface waters and bloom into billions of carbon dioxide-absorbing organisms — and light-detecting instruments on satellites map the swirls of their color.
This fall marks 20 years since NASA has continuously observed not just the physical properties of our planet, but the one thing that makes Earth unique among the thousands of other worlds we’ve discovered: Life.
Satellites measured land and ocean life from space as early as the 1970s. But it wasn't until the launch of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) in 1997 that the space agency began what is now a continuous, global view of both land and ocean life. A new animation captures the entirety of this 20-year record, made possible by multiple satellites, compressing a decades-long view of life on Earth into a captivating few minutes.
“These are incredibly evocative visualizations of our living planet,” said Gene Carl Feldman, an oceanographer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s the Earth, that is it breathing every single day, changing with the seasons, responding to the Sun, to the changing winds, ocean currents and temperatures."
Our Living Planet From Space
Video above: Since the fall of 1997, NASA satellites have continuously and globally observed all plant life at the surface of the land and ocean. Twenty years of satellite data has helped scientists track phytoplankton populations in the ocean, study changing vegetation in the Arctic reaches of North America, monitor crop yields and more. Video Credits: NASA's Goddard Space Flight Center.
The space-based view of life allows scientists to monitor crop, forest and fisheries health around the globe. But the space agency's scientists have also discovered long-term changes across continents and ocean basins. As NASA begins its third decade of global ocean and land measurements, these discoveries point to important questions about how ecosystems will respond to a changing climate and broad-scale changes in human interaction with the land.
Satellites have measured the Arctic getting greener, as shrubs expand their range and thrive in warmer temperatures. Observations from space help determine agricultural production globally, and are used in famine early warning detection. As ocean waters warm, satellites have detected a shift in phytoplankton populations across the planet's five great ocean basins — the expansion of "biological deserts" where little life thrives. And as concentrations of carbon dioxide in the atmosphere continue to rise and warm the climate, NASA's global understanding of plant life will play a critical role in monitoring carbon as it moves through the Earth system.
Life on Earth, from space
Animation above: From space, satellites can see Earth breathe. A new NASA visualization shows 20 years of continuous observations of plant life on land and at the
ocean’s surface, from September 1997 to September 2017. On land, vegetation appears on a scale from brown (low vegetation) to dark green (lots
of vegetation); at the ocean surface, phytoplankton are indicated on a scale from purple (low) to yellow (high). This visualization was created with
data from satellites including SeaWiFS, and instruments including the NASA/NOAA Visible Infrared Imaging Radiometer Suite and the Moderate Resolution Imaging Spectroradiometer. Video Credit: NASA.
Sixty years ago, people were not sure that Earth’s surface could be seen clearly from space. Many thought that the dust particles and other aerosols in the atmosphere would scatter the light, masking the oceans and continents, said Jeffrey Masek, chief of the Biospheric Sciences Laboratory at NASA Goddard.
The Gemini and Apollo programs demonstrated otherwise. Astronauts used specialized cameras to take pictures of Earth that show the beauty and complexity of our living planet, and helped kickstart the era of Earth science research from space. In 1972, the first Landsat mission began its 45-year record of vegetation and land cover.
“As the satellite archive expands, you see more and more dynamics emerging,” Masek said. “We’re now able to look at long-term trends.”
The grasslands of Senegal, for example, undergo drastic seasonal changes. Grasses and shrubs flourish during the rainy season from June to November, then dry up when the rain stops. With early weather satellite data in the 1970s and '80s, NASA Goddard scientist Compton Tucker was able to see that greening and die-back from space, measuring the chlorophyll in the plants below. He developed a way of comparing satellite data from two wavelengths, which gives a quantitative measurement of this greenness called the Normalized Difference Vegetation Index.
“We were astounded when we saw the first images. They were amazing because they showed how vegetation changed annually, year after year,” Tucker said, noting that others were surprised as well when the study came out in 1985. “When we produced this paper, people accused us of ‘painting by numbers,’ or fudging data. But for the first time, you could study vegetation from space based on their photosynthetic capacity.”
When the temperature is right, and water and sunlight are available, plants photosynthesize and produce vegetative material. Leaves strongly absorb blue and red light but reflect near-infrared light back into space. By comparing the ratio of red to near-infrared light, Tucker and his colleagues could quantify the vegetation covering the land.
Expanding these observations to the rest of the globe, the scientists could track the impact on plants of rainy and dry seasons elsewhere in Africa, see the springtime blooms in North America, and the after-effects of wildfires in forests worldwide.
But land is only part of the story. At the base of the ocean’s food web is phytoplankton — tiny organisms that, like land plants, turn water and carbon dioxide into sugar and oxygen, aided by the right combination of nutrients and sunlight.
Animation above: The SeaWiFS satellite was launched in late 1997, just in time to capture the phytoplankton that bloomed in the Eastern Equatorial Pacific as conditions changed from El Niño to La Niña, seen here in yellow. Animation Credit: NASA.
Satellites that can monitor the subtle changes in color of the ocean have helped scientists track changes in phytoplankton populations across the globe. The first view of ocean color came from the Coastal Zone Color Scanner, a proof-of concept instrument launched in 1979. Continuous observations of ocean color began with the launch of SeaWIFS in late 1997. The satellite was just in time to capture the transition from El Niño to La Niña conditions in 1998 — revealing just how quickly and dramatically phytoplankton respond to changing ocean conditions.
“The entire Eastern Pacific, from the coast of South America all the way to the dateline, transitioned from what was the equivalent of a biological desert to a thriving rainforest. And we watched it happen in real time,” Feldman said. “For me, that was the first demonstration of the power of this kind of observation, to see how the ocean responds to one of the most significant environmental perturbations it could experience, over the course of just a few weeks. It also showed that the ocean and all the life within it is amazingly resilient — if given half a chance.”
Tracking change from satellites
With 20 years of satellite data tracking ocean plant life on a global scale, scientists are investigating how habitats and ecosystems are responding to changing environmental conditions.
Recent studies of ocean life have shown that a long-term trend of rising sea surface temperatures is causing ocean regions known as “biological deserts” to expand. These regions of low phytoplankton growth occur in the center of large, slow-moving currents called gyres.
“As the surface waters warm, it creates a stronger boundary between the deep, cold, nutrient-rich waters and the sunlit, generally nutrient-poor surface waters,” Feldman said. This prevents nutrients from reaching phytoplankton at the surface, and could have significant consequences for fisheries and the marine ecosystem.
In the Arctic Ocean, an explosion of phytoplankton indicates change. As seasonal sea ice melts, warming waters and more sunlight will trigger a sudden, massive phytoplankton bloom that feeds birds, sea lions and newly hatched fish. But with warming atmospheric temperatures, that bloom is now happening several weeks early — before the animals are in place to take advantage of it.
“It’s not just the amount of food, it’s the location and timing that are just as critical,” Feldman said. “Spring bloom is coming earlier, and that’s going to impact the ecosystem in ways we don’t yet understand.”
The climate is warming fastest in Arctic regions, and the impacts on land are visible from space as well. The tundra of Western Alaska, Quebec and elsewhere is turning greener as shrubs extend their reach northwards.
The neighboring northern forests are changing as well. Massive fires in 2004 and 2015 wiped out millions of acres of forests in Alaska, including spruce forests, noted Chris Potter, a research scientist at NASA’s Ames Research Center in California’s Silicon Valley.
“These fires were amazing in the amount of forest area they burned and how hot they burned,” Potter said. “When the air temperature hits 90 degrees Fahrenheit in late May up there, and all these lightning strikes occurred, the forest burned very extensively — close to rivers, close to villages — and nothing could stop it.”
Animation above: Vegetation in North America wakes up in the spring, captured here as a change from pale green to dark green as photosynthesis ramps up with the season. White areas are covered in snow. Animation Credit: NASA.
Satellites help scientists routinely map fires, deforestation and other changes, and to analyze their impact on the carbon cycle, Potter said. Giant fires release many tons of carbon dioxide into the atmosphere, both from the charred trees and moss but also, especially in northern latitudes, from the soils. Potter and colleagues went to the burned areas of Central Alaska this year to measure the underlying permafrost — the thick mossy layer had burned off, exposing the previously frozen soils.
“It’s like taking the insulating layer off a cooler,” he said. “The ice melts underneath and it becomes a slushy mess.”
Forest types can change too, whether it’s after wildfires, insect infestations or other disturbance. The Alaskan spruce forests are being replaced with birch. Potter and his colleagues are also keeping an eye on California forests burned in recent fires, where the concern is that pines will be replaced by oaks.
“When drought is accentuated with these record high temperatures, nothing good seems to come from that for the existing forest type,” he said. “I think we’re seeing real clear evidence of climate causing land-cover change.”
Keeping an eye on crops
Changing temperatures and rainfall patterns also influence crops, whether they are grown in California or Africa. The “greenness” measurement that scientists use to measure forests and grasslands can also be used for agriculture, to monitor the health of fields throughout the growing season.
Researchers and policy makers realized this potential early. One of the first applications of Landsat data in the 1970s was to predict grain yields in Russia and better understand commodities markets. In 1985, food security analysts from USAID approached NASA to incorporate satellite images into their Famine Early Warning Systems Network, to identify regions where food production has been limited by drought. That partnership continues today. With rainfall estimates, vegetation measurements, as well as the recent addition of soil moisture information, NASA scientists can help organizations like USAID direct emergency help.
With improved data from Landsat, the MODIS instruments on NASA's Terra and Aqua spacecraft and other satellites, and by combining data from multiple sensors, researchers are now able to track the growth of crops in individual fields, Tucker said.
“This moves things down to the field sizes for probably 80 percent of the fields globally — this is a huge advancement,” Tucker said.
The view from space not only helps monitor crops, but can help improve agricultural practices as well. A winery in California, for example, uses individual pixels of Landsat data to determine when to irrigate and how much water to use.
Image above: Visualization from September 2017 showing plant life on land and at the ocean’s surface. On land, vegetation appears on a scale from brown (low vegetation) to dark green (lots of vegetation); at the ocean surface, phytoplankton are indicated on a scale from purple (low) to yellow (high). This visualization was created with data from satellites including SeaWiFS, and instruments including the NASA/NOAA Visible Infrared Imaging Radiometer Suite and the Moderate Resolution Imaging Spectroradiometer. Image Credit: NASA.
The next step for NASA scientists is actually looking at the process of photosynthesis from space. When plants undergo that chemical process, some of the absorbed energy fluoresces faintly back, notes Joanna Joiner, a NASA Goddard research scientist. With satellites that detect signals in the very specific wavelengths of this fluorescence, and a fine-tuned analysis technique that blocks out background signals, Joiner and her colleagues can see where and when plants start converting sunlight into sugars.
“It was kind of a revelation that yes, you can measure it,” Joiner said. An early study looked at the U.S. Corn Belt and found it fluoresces “like crazy,” she said. “Those plants have some of the highest fluorescence rates on Earth at their peak.”
Joiner and Tucker are using both the fluorescence data and vegetation indices to get the most information possible about plant growth at regional and global scales: “One of the big questions that still remains is how much carbon are the plants taking up, why does it vary year to year, and which areas are contributing to that variability,” Joiner said
Whether it’s crops, forests or phytoplankton blooms, NASA scientists are tracking life on Earth. Just as satellites help researchers study the atmosphere, rainfall and other physical characteristics of the planet, the ever-improving view from above will allow them to study the interconnected life of the planet, Feldman said.
“This is the capability that will allow us to understand how Earth’s biology responds to a changing planet,” he said.
Ames Research Center: https://www.nasa.gov/centers/ames/home/index.html
Goddard Space Flight Center: https://www.nasa.gov/centers/goddard/home/index.html
Animations (mentioned), Images (mentioned), Video (mentioned), Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Kate Ramsayer.
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Publié par Orbiter.ch à 16:56