Posted on by Nancy Atkinson

STEREO Maps Far Reaches of Solar System

NASA’s twin STEREO spacecraft have been studying the sun since their launch in 2006. But the mission made a surprising and unexpected discovery by detecting particles from the edge of the solar system, and for the first time, scientists have now been able to map the region where the hot solar wind meets up with the cold interstellar medium. However, this wasn’t done with optical instruments imaging in visible light, but by mapping the region by means of neutral, or uncharged, atoms. This breakthrough is a “new kind of astronomy using neutral atoms,” said Robert Lin, from the University of California Berkeley, and lead for the suprathermal electron sensor aboard STEREO. “You can’t get a global picture of this region, one of the last unexplored regions of the heliosphere, any other way because it is too tenuous to be seen by normal optical telescopes.” The findings also help clear up a discrepancy in the amount of energy in the region found by the Voyager 2 spacecraft as it passed through the edge of the solar system last year.

The heliosphere stretches from the sun to more than twice the distance of Pluto. Beyond its edge, called the heliopause, lies the relative quiet of interstellar space, at about 100 astronomical units (AU) – 100 times the Earth-sun distance. The termination shock is the region of the heliosphere where the supersonic solar wind slows to subsonic speed as it merges with the interstellar medium. The heliosheath is the region of churning plasma between the shock front and the interstellar medium.

The twin STEREO spacecraft, in Earth’s orbit about the sun, take stereo pictures of the sun’s surface and measure magnetic fields and ion fluxes associated with solar explosions.

Between June and October 2007, however, the suprathermal electron sensor in the IMPACT (In-situ Measurements of Particles and CME Transients) suite of instruments on board each STEREO spacecraft detected neutral atoms originating from both the shock front and the heliosheath beyond.

“The suprathermal electron sensors were designed to detect charged electrons, which fluctuate in intensity depending on the magnetic field,” said lead author Linghua Wang, a graduate student in UC Berkeley’s Department of Physics. “We were surprised that these particle intensities didn’t depend on the magnetic field, which meant they must be neutral atoms.”

UC Berkeley physicists concluded that these energetic neutral atoms were originally ions heated up in the termination that lost their charge to cold atoms in the interstellar medium and, no longer hindered by magnetic fields, flowed back toward the sun and into the suprathermal electron sensors on STEREO.

“This is the first mapping of energetic neutral particles from beyond the heliosphere,” Lin said. “These neutral atoms tell us about the hot ions in the heliosheath. The ions heated in the termination shock exchange charge with the cold, neutral atoms in the interstellar medium to become neutral, and then flow back in.”

According to Lin, the neutral atoms are probably hydrogen, since most of the particles in the local interstellar medium are hydrogen.

The findings from STEREO, reported in the July 3 issue of the journal Nature, clear up a discrepancy in the amount of energy dumped into space by the decelerating solar wind that was discovered last year when Voyager 2 crossed the solar system’s termination shock and entered the surrounding heliosheath.

The newly discovered population of ions in the heliosheath contains about 70 percent of the energy dissipated in the termination shock, exactly the amount unaccounted for by Voyager 2’s instruments, the UC Berkeley physicists concluded. The Voyager 2 results are reported in the same issue of Nature.

A new NASA mission, the Interstellar Boundary Explorer (IBEX), is planned for launch later this year to map more thoroughly the lower-energy energetic ions in the heliosheath by means of energetic neutral atoms to discover the structure of the termination shock and how hydrogen ions are accelerated there.

Original News Source: EurekAlert

Posted on by Nancy Atkinson

Proposed Mission Could Study Space-Time Around Black Holes

What do black holes, magnetars and supernovae have in common? They all emit X-rays. But it’s difficult, if not impossible to study certain aspects of the X-ray emissions from these powerful objects. And there’s much we don’t understand about how black holes distort space-time around them, or how magnetars affect their surroundings, or how cosmic rays are accelerated by shocks in supernova remnants. A proposed new NASA mission called Gravity and Extreme Magnetism (GEMS), will use a new technique to study what has been unattainable until now. GEMS won’t study the X-ray emission of these objects directly, but will build up a picture indirectly by measuring the polarization of X-rays emitted from these violent regions.


No current mission has resolution to do this, or in the case of magnetic field imaging, simply can’t do this because magnetic fields are invisible.

X-rays are very powerful, and like all light, X-rays have a vibrating electric field. When light travels freely through space, it can vibrate in any direction. However, under certain conditions, it becomes polarized, meaning it is forced to vibrate in only one direction. This happens when light scatters off of a surface, for example.

In a similar manner, we use polarized glasses to reduce road glare. The glare is simply light that has become polarized by scattering off the road. The glasses are made to block polarized light, so they eliminate the glare.

“GEMS will be the first mission designed just to measure the polarization of these X-rays, which will enable us to explore these exotic places in an unprecedented way,” said GEMS Principal Investigator Dr. Jean Swank of NASA’s Goddard Space Flight Center in Greenbelt, Md.
GEMS was proposed as part of NASA’s Explorer program, and was selected as one of six missions for a detailed concept study. NASA will select two of the six for development in the spring of 2009. One selected mission is scheduled to launch in 2012, and the other is planned for launch in 2015.

“GEMS will be able to tell the shapes of the X-ray-emitting matter trapped near black holes better than existing missions can — in particular, whether matter around a black hole is confined to a flat disk or puffed into a sphere or squirting out in a jet,” said Swank.

“Since X-rays are polarized by the space swirling around a spinning black hole, GEMS also provides a method of determining black hole spin independent of other techniques, which is needed to check their accuracy,” said Swank.

The heart of GEMS will be a small chamber filled with gas. As X-rays travel through the gas, they release a cloud of electrons along their path. Since the electrons tend to move in the same direction as the electric field produced by the X-ray, the instrument will measure the electron cloud to get the direction of the X-ray’s electric field, which is the same as its polarization.

Original News Source: PhysOrg

Posted on by Nancy Atkinson

Hubble Does Independence Day With Stars and Stripe

Back in 1006 A.D, observers from Africa to Europe to the Far East witnessed and recorded the arrival of light from what is now called SN 1006, a tremendous supernova explosion caused by the final death throes of a white dwarf star nearly 7,000 light-years away. One Egyptian astronomer recorded the object was 2 – 3 times as large as the disc of Venus and about one quarter the brightness of the moon. The supernova was probably the brightest star ever seen by humans, visible even during the day for weeks, and it remained visible to the naked eye for at least two and a half years before fading away. Remnants of this supernova are still visible to telescopes, and the Hubble Space Telescope captured this close-up a filament of the shock wave of the explosion, still reverberating through space, seen here against the grid of background stars. The full image of SN 1006 is pretty impressive, too…

SN 1006 has a diameter of nearly 60 light-years, and it is still expanding at roughly 6 million miles per hour. Even at this tremendous speed, however, it takes observations typically separated by years to see significant outward motion of the shock wave against the grid of background stars. In the Hubble image shown here, the supernova would have occurred far off the lower right corner of the image, and the motion would be toward the upper left.

It wasn’t until the mid-1960s that radio astronomers first detected a nearly circular ring of material at the recorded position of the supernova. The ring was almost 30 arcminutes across, the same angular diameter as the full moon. The size of the remnant implied that the blast wave from the supernova had expanded at nearly 20 million miles per hour over the nearly 1,000 years since the explosion occurred.

In 1976, the first detection of exceedingly faint optical emission of the supernova remnant was reported, but only for a filament located on the northwest edge of the radio ring. A tiny portion of this filament is revealed in detail by the Hubble observation. The twisting ribbon of light seen by Hubble corresponds to locations where the expanding blast wave from the supernova is now sweeping into very tenuous surrounding gas.

The hydrogen gas heated by this fast shock wave emits radiation in visible light. Hence, the optical emission provides astronomers with a detailed “snapshot” of the actual position and geometry of the shock front at any given time. Bright edges within the ribbon correspond to places where the shock wave is seen exactly edge on to our line of sight.

Original News Source: HubbleSite

Posted on by Nancy Atkinson

Solar Sail To Launch This Summer

NanoSail D. Image credit NASA

NASA’s Marshall and Ames Research Centers will team up with the commercial space company SpaceX to launch and deploy a solar sail this summer. A bread-box sized payload called NanoSail-D will travel to space onboard a SpaceX Falcon 1 Rocket and if all goes well, it will be the first fully deployed solar sail in space, and the first spacecraft to use a solar sail as a primary means of orbital maneuvering. The first launch window is from July 29th to August 6th, with a back-up window extending from August 29th to September 5th. Weighing less than 4.5 kilograms (10 pounds) the aluminum and plastic sail has about 9.3 m² (100 square feet) of light-catching surface which researchers hope will successfully propel the spacecraft.

Solar sails have been the stuff of dreams for years. Because there’s no friction in space, once a solar sail starts moving, it can go on forever. While rockets would run out of gas and begin to coast, a spaceship powered by solar sails would continue accelerating as long as there is a solar wind, reaching faster speeds and covering distances far greater than any rocket. No rocket has been invented that could carry enough fuel to reach the outer solar system in as short a time. And like a marine sail, a solar sail could also bring you home. You could use the solar sail to travel “against the wind,” back to Earth.

“It’s not so much about how far a sail will go compared to a rocket; the key is how fast,” says Edward “Sandy” Montgomery of NASA’s Marshall Space Flight Center. “The Voyagers have escaped the solar system, and they were sent by rockets, but it’s taken more than three decades to do it. A sail launched today would probably catch up with them in a single decade. Sails are slower to get started though. So, for example, between the Earth and the moon, rockets might be preferred for missions with a short timeline. It’s a trip of days for rockets, but months for a solar sail. The rule of thumb, therefore, would be to use rockets for short hops and solar sails for the long hauls.”

Previous attempts to launch and deploy a solar sail in space have met limited success. In 2004 Japan launched prototype solar sails that deployed, but they weren’t used for propulsion. The Planetary Society attempted a solar sail launch in 2005, called Cosmos 1, but the Russian launch vehicle failed to reach orbit. NASA did successfully deploy a solar sail in a vacuum chamber in 2004, but of course, its propulsive capability wasn’t able to be tested.

Montgomery believes a successful mission would be huge for the future of spaceflight. If successful, solar sails could potentially help with a growing problem of space debris.

“Currently, micro-satellites in orbit above a few hundred kilometers can stay in orbit for decades after completing their mission,” Montgomery said. “This creates an orbital debris collision risk for other spacecraft. NanoSail-D will demonstrate the feasibility of using a drag sail to decrease the time satellites clutter up Earth’s orbit. Although our sail looks like a kite, it will act like a parachute (or like a drag sail) in the very thin upper atmosphere around Earth. It will slow the spacecraft and make it lose altitude, re-enter the Earth’s atmosphere and burn off in a relatively short period of time. A drag sail is a lighter alternative to carrying a propulsion system to de-orbit a satellite.”

Movie of how NanoSail D will unfurl.

Original News Source: Science at NASA

Posted on by Nancy Atkinson

Cassini Primary Mission Complete; Ready to Tackle New Assignments

An aurora dances on Saturn in this image from the Cassini orbiter. Credit: NASA/JPL/University of Arizona

Saturn’s gorgeous rings. Geysers on Enceladus. Methane lakes on Titan. These are just a few of the images that stand out from the Cassini mission’s four year survey of Saturn and its remarkable system of rings and moons. On June 30 the Cassini spacecraft completes its primary mission at the ringed planet, and now will embark on an extended two year mission, with hopes of studying more closely the most intriguing targets, Titan and Enceladus and the interaction between Saturn’s icy moons and rings.

“We’ve had a wonderful mission and a very eventful one in terms of the scientific discoveries we’ve made, and yet an uneventful one when it comes to the spacecraft behaving so well,” said Bob Mitchell, Cassini program manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We are incredibly proud to have completed all of the objectives we set out to accomplish when we launched. We answered old questions and raised quite a few new ones and so our journey continues.”
Mitchell said while its clear Cassini isn’t just driving off the showroom floor, considering how complex the nature of the mission has been and how long it’s been going, the spacecraft is doing remarkably well.

Cassini launched Oct. 15, 1997, taking seven years to traverse 3.5 billion kilometers (2.2 billion miles) to Saturn. The mission entered Saturn’s orbit on June 30, 2004, and began returning stunning data of Saturn’s rings almost immediately.

Mitchell said the spacecraft has made major discoveries about the dynamics of the rings, and how the moons gravity shapes the rings into the different gaps. “The geysers of Enceladus rank near the top of the excitement of the discoveries that we’ve made,” he said. “ Titan is very different than we expected it to be. It’s a lot like Earth, if you just replace water with methane there a lot of processes on Titan that look like Earth.”

The extended mission will allow for monitoring seasonal effects on Titan and Saturn, exploring new places within Saturn’s magnetosphere, and observing the unique ring geometry of the Saturn equinox in August of 2009 when sunlight will pass directly through the plane of the rings.

The next two years, Cassini will have 26 more encounters with Titan, seven close encounters with Enceladus, and one each with the icy moons Dione, Rhea and Helene.

And there’s sure to be other discoveries at Saturn as well. “There are a number of surprises yet waiting for us, as the seasons change, we’re bound to find exciting things we haven’t even thought of yet,” said Mitchell.

Original News Source: JPL

Posted on by Nancy Atkinson

SOHO the Comet-Finder — And You Can Help

On June 25th, the ESA/NASA SOHO spacecraft discovered its 1,500th comet, making it more successful than all other comet discoverers throughout history, combined. But wait a minute, SOHO is the Solar and Heliospheric Observatory, designed to study solar physics. What’s it doing looking for comets? SOHO just happens to have a great vantage point to see comets as they approach the sun. Since its orbit is situated between the Sun and Earth, it has a unique view of the regions close to the sun that we can rarely see from Earth. But SOHO’s comet-finding success is just an added benefit to the extraordinary revelations this spacecraft has provided in its 13 years in space, observing the Sun and the near-Sun environment. “Catching the enormous total of comets has been an unplanned bonus,” said Bernhard Fleck, ESA SOHO Project Scientist.

About 85% of SOHO’s comet discoveries are fragments from a once-great comet that split apart in a death plunge around the Sun, probably many centuries ago. The fragments are known as the Kreutz group, which now pass within 1.5 million km of the Sun’s surface when they return from deep space.

That’s pretty close in celestial terms, and from Earth, we can only see those regions close to the Sun during an eclipse.

But that also puts them within sight of SOHO’s electronic eyes. Images of the comets are captured by the Large Angle and Spectrometric Coronograph (LASCO), one of 12 instruments on board.

Of course, LASCO itself does not make the detections; that task falls to an open group of highly-skilled volunteers who scan the data as soon as it is downloaded to Earth. Once SOHO transmits to Earth, the data can be on the Internet and ready for analysis within 15 minutes.

Enthusiasts from all over the world look at each individual image for a tiny moving speck that could be a comet. When someone believes they have found one, they submit their results to Karl Battams at the Naval Research Laboratory, Washington DC, who checks all of SOHO’s findings before submitting them to the Minor Planet Center, where the comet is cataloged and its orbit calculated.

From this mission, and with the public’s help, scientists have learned a great deal about comets.

“This is allowing us to see how comets die,” says Battams. When a comet constantly circles the Sun, it loses a little more ice each time, until it eventually falls to pieces, leaving a long trail of fragments. Thanks to SOHO, astronomers now have a plethora of images showing this process. “It’s a unique data set and could not have been achieved in any other way,” says Battams.

Most of the comet fragments are eventually destroyed when they get close enough to the Sun, evaporated by the Sun’s radiation.

Interested in helping search for SOHO’s comets? Visit the Sungrazing comets page.

Original News Source: ESA

Posted on by Nancy Atkinson

Launch Pad Repairs to Begin; Hubble Repair Mission Should Go As Scheduled

Work will begin on Friday to repair damaged sections of Kennedy Space Center’s launch pad 39A that was damaged during the last space shuttle launch on May 31. On Thursday, (June 26) NASA managers approved a plan that would complete the repairs by the third week of August. Therefore the mission schedule shouldn’t be impacted. The next space shuttle flight, the high-profile final mission to repair the Hubble Space Telescope is scheduled to launch on October 8, and if all goes well with the repairs, space shuttle Atlantis would crawl its way out to the pad on August 29. “We really like the plan,” said shuttle Program Manager John Shannon. “We expect to start moving out on it right away.”

During shuttle Discovery’s launch in May more than 3,500 fire-resistant bricks lining the northeast wall of the “flame trench” at pad 39A were blasted away. Radar tracking showed some of the bricks shot out of the trench at about 1,000 feet per second, or about 680 mph. But NASA officials said the incident did not pose a threat to the space shuttle. Computer simulations run by engineers showed that none of the bricks flew up near the pad surface, and therefore couldn’t have hit the shuttle.

“It’s not a flight [safety] issue at all,” said Rita Willcoxon, space shuttle processing manager, during a teleconference on Thursday.

The work is estimated to cost less than $2.7 million.
A detailed inspection found that many of the anchor plates used to secure the interlocking fire bricks to the 3-foot-thick concrete back wall were heavily eroded due to decades of exposure to severe pressures and acidic rocket exhaust. Additionally, epoxy used to help secure the bricks to the wall was degraded or not consistently applied when the pad was built in the mid 1960s. As a result, the outer brick wall was not tightly locked to the underlying concrete wall it was designed to protect.

To fix the trench, a two different sections of the trench wall will be stripped of bricks.. A steel mesh-like structure will be erected over the exposed backwall and then covered in sprayed-on Fondu Fyre, a material used to protect the massive flame deflector directly under the shuttle’s boosters and main engines.

Working two 10-hour shifts per day, the repair team expects to have the brick removed by July 19. After that, the mesh will be erected and the Fondue Fyre applied.
Officials said the repaired flame trench will be inspected after every launch, but is expected to hold up through the end of shuttle operations in 2010.

The other shuttle pad, 39B may have similar deficiencies in its flame trench. But no major repairs are scheduled for that pad, as all 10 remaining shuttle flights are scheduled to use pad 39A. NASA will have a shuttle ready at 39B for a rescue mission should Atlantis suffer major damage during the Hubble flight, since the shuttle couldn’t reach the International Space Station as a safe haven, which is in a different orbit than Hubble.

News Sources: CBS News Space Place, Space.com

Posted on by Nancy Atkinson

Twin Spiral Galaxies Dance Together

This incredible image looks like space art, or a trick done with Photoshop, but its an actual image of twin galaxies dancing together in the sky. The image was obtained, appropriately enough by the Gemini South telescope in Chile using GMOS, the Gemini Multi-Object Spectrograph. These two nearly identical spiral galaxies are in Virgo, 90 million light years distant, in the early stages of a gentle gravitational embrace.

Like two dancers grabbing hands while passing, NGC 5427 (the nearly open-faced spiral galaxy at lower left) and its southern twin NGC 5426 (the more oblique galaxy at upper right), are in the throes of a slow but disturbing interaction – one that could take a hundred million years to complete.

At a glance, these twin galaxies — which have similar masses, structures, and shapes and are together known as Arp 271 – appear undisturbed. But recent studies have shown that the mutual pull of gravity has already begun to alter and distort their visible features.

Typically, the first sign of a galaxy interaction is the formation of a bridge-like feature. Indeed, the two spiral arms on the western (upper) side of NGC 5426 appear as long appendages that connect with NGC 5427. This intergalactic bridge acts like a feeding tube, allowing the twins to share gas and dust with one other across the 60,000 light years (less than one galaxy diameter) of space separating them.

Colliding gases caused by the interaction may have also triggered bursts of star formation (starbursts) in each galaxy. Star-forming, or HII, regions appear as hot pink knots that trace out the spiral patterns in each galaxy. HII regions are common to many spiral systems, but the giant ones in NGC 5426 are curiously knotted and more abundant on the side of the galaxy closest to NGC 5427. Starburst activity can also be seen in the galaxy’s connecting bridge.

Once thought to be unusual and rare, gravitational interactions between galaxies are now known to be quite common (especially in densely populated galaxy clusters) and are considered to play an important role in galaxy evolution. Most galaxies have probably had at least one major, if not many minor, interactions with other galaxies since the advent of the Big Bang some 13 billion years ago. Our own Milky Way, a spiral galaxy like those in this image, is, in fact, performing its own stately dance. Both with the nearby dwarf galaxy, called the Large Magellanic Cloud and a future interaction with the large spiral galaxy M-31 or the Great Andromeda Galaxy, which is now located about 2.6 million light years away from the Milky Way. This new Gemini image is possibly a preview of things to come for our own galaxy. Ultimately the end result of these types of collisions will be a large elliptical galaxy.

Original news source: Gemini Observatory

Posted on by Nancy Atkinson

Two Faces of Mars Explained

Mars has two faces. No, not those kind of faces, but the notable differences between the northern and southern hemisphere. Mars has lowlands in the north and highlands in the south. This disparity has long puzzled planetary scientists, but most concurred that early in Mars history, impacts shaped the planet’s two-faced landscape. But many disagreed whether several small impacts or one big one were responsible for sculpting Mars’ surface. Now scientists at the California Institute of Technology have shown through computer modeling that the Mars dichotomy, as the divided terrain has been termed, can indeed be explained by one giant impact early in the planet’s history.

“The dichotomy is arguably the oldest feature on Mars,” said Oded Aharonson from Caltech. Scientists believe the differences in hemispheric features arose more than four billion years ago.

Previously, scientists discounted the idea that a single, giant impactor created the lower elevations and thinner crust of Mars’s northern region, says Margarita Marinova, a graduate student at Caltech, and one of the lead authors of the study.

For one thing, Marinova explained, it was thought that a single impact would leave a circular footprint, but the outline of the northern lowlands region is elliptical. There is also a distinct lack of a crater rim: topography increases smoothly from the lowlands to the highlands without a lip of concentrated material in between, as is the case in small craters. Finally, it was believed that a giant impactor would obliterate the record of its own occurrence by melting a large fraction of the planet and forming a magma ocean.

“We set out to show that it’s possible to make a big hole without melting the majority of the surface of Mars,” Aharonson says. The team modeled a range of projectile parameters that could yield a cavity the size and ellipticity of the Mars lowlands without melting the whole planet or making a crater rim.

The team ran over 500 computer simulations combining various energies, velocities, and impact angles. Finally, they were able to narrow in on a “sweet spot”–a range of single-impact parameters that would make exactly the type of crater found on Mars. Their dedicated supercomputer allowed them to run simulations not run in the past. “The ability to search for parameters that allow an impact compatible with observations is enabled by the dedicated machine at Caltech,” Aharonson said.

The favored simulation conditions outlined by the sweet spot suggest an impact energy of around 1029 joules, which is equivalent to 100 billion gigatons of TNT. The impactor would have hit Mars at an angle between 30 and 60 degrees while traveling at 6 to 10 kilometers per second. By combining these factors, Marinova calculated that the projectile was roughly 1,600 to 2,700 kilometers across.

Estimates of the energy of the Mars impact place it squarely between the impact that is thought to have led to the extinction of dinosaurs on Earth 65 million years ago and the one believed to have extruded our planet’s moon four billion years ago.

Marinova said the timing of formation of our moon and the Mars dichotomy is not coincidental. “This size range of impacts only occurred early in solar system history,” she says. The results of this study are also applicable to understanding large impact events on other heavenly bodies, like the Aitken Basin on the moon and the Caloris Basin on Mercury.

This report, published in the June 26 issue of Nature, goes along with two other papers on the Mars dichotomy. One published by Jeffrey Andrews-Hanna and Maria Zuber of MIT and Bruce Banerdt of JPL examine the gravitational and topographic signature of the dichotomy with information from the Mars orbiters. Another accompanying report, from a group at UC Santa Cruz led by Francis Nimmo, explores the expected consequences of mega-impacts.

Original News Source: EurekAlert

Posted on by Nancy Atkinson

Mars Atmosphere Once Held Enough Moisture for Dew or Drizzle

Data from Mars orbiters and landers have suggested that any past water on the Red Planet’s surface probably came from subsurface moisture bubbling up from underground. But a new study of Martian soil data implies that Mars’ atmosphere was once thick enough to hold moisture and that dew or even drizzle hit the ground. Geoscientists at the University of California Berkeley combined data from the Viking 1 and 2 landers, the Pathfinder rover, and the current rovers Spirit and Opportunity. The scientists say tell-tale signs of this type of moisture are evident on the planet’s surface.

“By analyzing the chemistry of the planet’s soil, we can derive important information about Mars’ climate history,” said Ronald Amundson, UC Berkeley professor of ecosystem sciences and the study’s lead author. “The dominant view, put forward by many now working on the Mars missions, is that the chemistry of Mars soils is a mix of dust and rock that has accumulated over the eons, combined with impacts of upwelling groundwater, which is almost the exact opposite of any common process that forms soil on Earth. In this paper, we try to steer the discussion back by re-evaluating the Mars data using geological and hydrological principles that exist on Earth.”

The team says soil at the various spacecraft landing sites have lost significant fractions of the elements that make up the rock fragments from which the soil was formed. This is a sign, they say, that water once moved downward through the dirt, carrying the elements with it. Amundson also pointed out that the soil also shows evidence of a long period of drying, as evidenced by surface patterns of the now sulfate-rich land. The distinctive accumulations of sulfate deposits are characteristic of soil in northern Chile’s Atacama Desert, where rainfall averages approximately 1 millimeter per year, making it the driest region on Earth.

Researchers compared images such as this image of the Atacama Desert with the above image taken by the Opportunity rover on Mars, which show similar surface patterns.

“The Atacama Desert and the dry valleys of Antarctica are where Earth meets Mars,” said Amundson. “I would argue that Mars has more in common geochemically with these climate extremes on Earth than these sites have in common with the rest of our planet.”

Amundson noted that sulfate is prevalent in Earth’s oceans and atmosphere, and is incorporated in rainwater. However, it’s so soluble that it typically washes away from the surface of the ground when it rains. The key for the distinctive accumulation in soil to appear is for there to be enough moisture to move it downward, but not so much that it is washed away entirely.

The researchers also noted that the distribution of the chemical elements in Martian soil, where sulfates accumulate on the surface with layers of chloride salt underneath, suggest atmospheric moisture.

“Sulfates tend to be less soluble in water than chlorides, so if water is moving up through evaporation, we would expect to find chlorides at the surface and sulfates below that,” said Amundson. “But when water is moving downward, there’s a complete reversal of that where the chlorides move downward and sulfates stay closer to the surface. There have been weak but long-term atmospheric cycles that not only add dust and salt but periodic liquid water to the soil surface that move the salts downward.”

Amundson pointed out that there is still debate among scientists about the degree to which atmospheric and geological conditions on Earth can be used as analogs for the environment on Mars. He said the new study suggests that Martian soil may be a “museum” that records chemical information about the history of water on the planet, and that our own planet holds the key to interpreting the record.

“It seems very logical that a dry, arid planet like Mars with the same bedrock geology as many places on Earth would have some of the same hydrological and geological processes operating that occur in our deserts here on Earth,” said Amundson. “Our study suggests that Mars isn’t a planet where things have behaved radically different from Earth, and that we should look to regions like the Atacama Desert for further insight into Martian climate history.”

Original News Source: EurekAlert