Category: Mars

Image credit: NASA/JPL
During Tuesday’s NASA mission briefing on progress with the rover at Meridiani Planum, Mars Exploration Rover (MER) principal invesigator, Steve Squyres introduced not just startling new water evidence, but another new piece to the bigger astrobiological puzzle: water and sulfur. “With this quantity of sulfate [up to forty percent sulfur salts at some places near the Opportunity landing site], you kind of have to have water involved.”

But water is just the first puzzle piece in any future biological picture for the red planet, according to mission scientists. This sentiment was underscored by considering just a few of the puzzle pieces still missing. Time for instance is one element yet to be considered. “We know that the essential major and minor biogenic elements exist on Mars,” wrote Rocco Mancinelli , a SETI Institute scientist, “The primary factor in determining if life could have arisen on Mars lies in determining if liquid water existed on its surface for sufficient time. The history of water lies within the mineralogy of the rocks.”

Habitability and Energy
But now that some local portions of Mars show mineralogical promise of just such water at least temporarily ‘soaked’ into their geological record, what other key ingredients might be needed next, particularly to have supported a convincing case for ancient habitability? The tough question begs for a comparison to what microbiologists know about life on Earth, so one must begin with a simpler experiment: How would a hardy Earth microbe survive today on Mars?

Not particularly well, according to most microbiologists. The compound problems of low temperatures, low pressures, and scarce energy are multifold on today’s Mars, even when ‘today’ is taken to include the last tens of millions of years in Mars’ meteorological history.

Compared to the Earth’s average temperature of 15 C (59 F), Mars globally has an average temperature of -53 C (-63.4 F). While transient temperatures do occasionally rise above water’s freezing point in the equatorial regions around both landing sites, most biological scenarios need a booster shot of basic warmth. A habitable case for the red planet usually posits a long-lost Mars–one that was both wetter and warmer than what might seem hostile to even the hardiest lifeforms known today.

The Next Generation of Better Microbes, Desulfotomaculum
But once a water source is identified, perhaps the bigger immediate problem on Mars is the very thin and unbreathable atmosphere, one that is a mere one percent of Earth’s sea level pressure. If exposed on the surface, a microbe on Mars today would quickly dessicate and freeze. That is, unless it could pull off some kind of hibernation once the environment turned extreme to its favored biology. A promising microbial candidate must evolve some means to sporulate, as it would prove a big plus to hibernate during long periods whenever Martian weather turned inhospitable.

Scientists intrigued by ancient–and so far, local– water evidence uncovered near the Opportunity site have posed the speculative question: would spore-forming, sulfate-reducing bacteria offer a new model organism for the next generation of Mars’ microbe hunters?

According to one veteran Viking and MER science team member, Benton Clark, one such candidate has been a leading contender for weathering the harsh martian conditions that could otherwise fatally stress a microbe. Clark, of Lockheed Martin in Denver, said “I’ve always had a favorite organism, Desulfotomaculum, which is an organism that can live off sulfate, as we find in these rocks.”

Since 1965, when the spore-former was first discovered and classified, its biology has offered some of the best extremes for microbial survivability. Living without sunlight while forming spores when the weather gets cold or dry could make this hardy organism a model to consider among future planetary scientists.

Primitive Solar Energy Independence
Loosely, the name Desulfotomaculum means a ‘sausage’ that reduces sulfur compounds. It is a rod-shaped organism; the Latin, -tomaculum, means ‘sausage’. Desulfotomaculum is an anaerobe, meaning it does not require oxygen. Terrestrially, it is found in soil, water, and geothermal regions, and in the intestines of insects and animal rumens. Its lifecycle depends on reducing sulfur compounds like magnesium sulfate (or epsom salts) to hydrogen sulfide.

The sulfur-metabolizing microbes use a very primitive form of energy generation: their chemical action is as important as their immediate habitat. From what we know about conditions on the early Earth, it was probably hot, and there was a lot of ultraviolet (UV). It was a reducing atmosphere, so things like hydrogen sulfide as an inorganic source of energy are probably what was available to use. On Earth, some Desulfotomaculum species grow optimally at 30-37 C but can grow at other temperatures depending on which of the nearly 20 species of Desulfotomaculum is being cultured.

On the frigid, dry planet so far from the Sun, anything that metabolizes successfully would also benefit from some novel pathways other than photosynthesis to produce energy. Surprisingly while certain kinds of radiation hazards on Mars can be treacherous, the lack of UV sunlight itself is an immediate problem. What kind and intensity of sunlight might be most useful to common green or chlorophyll-rich life on Earth? Or when might a microbe thrive only with helpful shade from soil coverage or a dark rocky overhang. Doing without direct sunlight might be a Martian norm.

“[Desulfotomaculum] needs some hydrogen to go with that, but [sulfur] is its energy source. It can work independent of the sun,” said Clark. “The reason I like the latter organism is because it can form spores as well, so it can hibernate over these interim times on Mars between the warmer spells and the differences in [solar] obliquity that we know about.”

“So in addition to physical evidence of fossils,” said Clark, “you can have chemical evidence. It turns out that sulfur is one of those tracers that work out quite well in isotopic fractionation. When living organisms process sulfur, they tend to fractionate isotopes differently from geological or mineralogical ways…So there are organisms and isotopic ways to look for it. To do the isotopic analysis, you’re probably going to have the samples back on Earth.”

Preserving Life
MIT geologist, John Grotzinger, took up the challenging question of how a future mission planner might begin to formulate an overall biological strategy. After successfully landing near this kind of outcrop at the Opportunity site, can a future Mars’ mission look for evidence of fossil life? “The answer to this question is very simple. On Earth, which is the only experience that we have, finding fossils preserved in ancient rocks is very rare. You have to do everything you can to optimize the situation for their preservation.”

From the outset of the Opportunity mission, Andrew Knoll, a Harvard paleontologist and member of the MER science team told Astrobiology Magazine that, “The real question that one wants to keep in mind when thinking about Meridiani is: What, if any, signatures of that biology actually get preserved in diagenetically stable rocks? ..If water is present on the Martian surface for 100 years every 10 million years, that’s not very interesting for biology. If it’s present for 10 million years, that’s very interesting.”

“You worry first about preservation,” emphasized Grotzinger. “You target your strategy to optimize preservation. If something was there, these [conditions can be] ideal for time capsules…but it is something of a challenge. …We want to urge caution in interpreting these results at this point.”

“Stay tuned,” concluded Squyres.

Original Source: NASA/Astrobiology Magazine

Image credit: NASA/JPL
Scientists have concluded the part of Mars that NASA’s Opportunity rover is exploring was soaking wet in the past.

Evidence the rover found in a rock outcrop led scientists to the conclusion. Clues from the rocks’ composition, such as the presence of sulfates, and the rocks’ physical appearance, such as niches where crystals grew, helped make the case for a watery history.

“Liquid water once flowed through these rocks. It changed their texture, and it changed their chemistry,” said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science instruments on Opportunity and its twin, Spirit. “We’ve been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion.”

Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA Headquarters, Washington, said, “NASA launched the Mars Exploration Rover mission specifically to check whether at least one part of Mars ever had a persistently wet environment that could possibly have been hospitable to life. Today we have strong evidence for an exciting answer: Yes.”

Opportunity has more work ahead. It will try to determine whether, besides being exposed to water after they formed, the rocks may have originally been laid down by minerals precipitating out of solution at the bottom of a salty lake or sea.

The first views Opportunity sent of its landing site in Mars’ Meridiani Planum region five weeks ago delighted researchers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., because of the good fortune to have the spacecraft arrive next to an exposed slice of bedrock on the inner slope of a small crater.

The robotic field geologist has spent most of the past three weeks surveying the whole outcrop, and then turning back for close-up inspection of selected portions. The rover found a very high concentration of sulfur in the outcrop with its alpha particle X-ray spectrometer, which identifies chemical elements in a sample. “The chemical form of this sulfur appears to be in magnesium, iron or other sulfate salts,” said Dr. Benton Clark of Lockheed Martin Space Systems, Denver. “Elements that can form chloride or even bromide salts have also been detected.”

At the same location, the rover’s Moessbauer spectrometer, which identifies iron-bearing minerals, detected a hydrated iron sulfate mineral called jarosite. Germany provided both the alpha particle X- ray spectrometer and the Moessbauer spectrometer. Opportunity’s miniature thermal emission spectrometer has also provided evidence for sulfates.

On Earth, rocks with as much salt as this Mars rock either have formed in water or, after formation, have been highly altered by long exposures to water. Jarosite may point to the rock’s wet history having been in an acidic lake or an acidic hot springs environment.

The water evidence from the rocks’ physical appearance comes in at least three categories, said Dr. John Grotzinger, sedimentary geologist from the Massachusetts Institute of Technology, Cambridge: indentations called “vugs,” spherules and crossbedding.

Pictures from the rover’s panoramic camera and microscopic imager reveal the target rock, dubbed “El Capitan,” is thoroughly pocked with indentations about a centimeter (0.4 inch) long and one-fourth or less that wide, with apparently random orientations. This distinctive texture is familiar to geologists as the sites where crystals of salt minerals form within rocks that sit in briny water. When the crystals later disappear, either by erosion or by dissolving in less-salty water, the voids left behind are called vugs, and in this case they conform to the geometry of possible former evaporite minerals.

Round particles the size of BBs are embedded in the outcrop. From shape alone, these spherules might be formed from volcanic eruptions, from lofting of molten droplets by a meteor impact, or from accumulation of minerals coming out of solution inside a porous, water-soaked rock. Opportunity’s observations that the spherules are not concentrated at particular layers in the outcrop weigh against a volcanic or impact origin, but do not completely rule out those origins.

Layers in the rock that lie at an angle to the main layers, a pattern called crossbedding, can result from the action of wind or water. Preliminary views by Opportunity hint the crossbedding bears hallmarks of water action, such as the small scale of the crossbedding and possible concave patterns formed by sinuous crestlines of underwater ridges.

The images obtained to date are not adequate for a definitive answer. So scientists plan to maneuver Opportunity closer to the features for a better look. “We have tantalizing clues, and we’re planning to evaluate this possibility in the near future,” Grotzinger said.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington.

For information about NASA and the Mars mission on the Internet, visit http://www.nasa.gov. Images and additional information about the project are also available at http://marsrovers.jpl.nasa.gov and http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Image credit: NASA/JPL
Spirit Status for sol 55
Spirit used its rock abrasion tool for brushing the dust off three patches of a rock called “Humphrey,” during its 55th sol on Mars, ending at 5:53 p.m. Saturday, PST. Before applying the wire-bristled brush, the rover inspected the surface of the rock with its microscope and with its alpha particle X-ray spectrometer, which identifies elements that are present. Brushing three different places on a rock one right after another was an unprecedented use of the rock abrasion tool, designed to provide a larger cleaned area for examining.

Afterwards, Spirit rolled backward 85 centimeters (2.8 feet) to a position from which it could use its miniature thermal emission spectrometer on the cleaned areas for assessing what minerals are present. Due to caution about potential hazards while re-approaching “Humphrey,” the rover moved only part of the way back. Plans for sol 56, ending at 6:33 p.m. Sunday, PST, call for finishing that re-approach and further inspecting the brushed areas. If all goes well, the rock abrasion tool’s diamond-toothed grinding wheel will cut into the rock on sol 57 to expose fresh interior material.

For wake-up music on sol 55, controllers chose “Brush Your Teeth,” by Cathy Fink and Marcy Marxer, and “Knock Three Times,” by Tony Orlando and Dawn.

Opportunity Status for sol 35
During its 35th sol on Mars, ending at 6:14 a.m. Sunday, PST, Opportunity manipulated the microscopic imager at the tip of its arm for eight observations of the fine textures of an outcrop-rock target called “Guadalupe.” The observations include frames to be used for developing stereo and color views.

Opportunity also used its Moessbauer spectrometer and, after an overnight switch, its alpha particle X-ray spectrometer to assess the composition of the interior material of “Guadalupe” exposed yestersol by a grinding session with the rock abrasion tool.

The panoramic camera up on the rover’s mast captured a new view toward the eastern horizon beyond the crater where Opportunity is working, for use in evaluating potential drive directions after the rover leaves the crater.

Jimmy Cliff’s “I Can See Clearly Now,” was played in the mission support area at JPL as Opportunity’s sol 35 wake-up music.

Plans for sol 36, ending at 6:54 a.m. Monday, PST, called for finishing the close-up inspection of “Guadalupe,” then backing up enough to give the panoramic camera and miniature emission spectrometer good views of the area where the rock interior has been exposed by grinding.

Original Source: NASA/JPL News Release

Image credit: Joint Astronomy Center
Astronomers have detected hydrogen peroxide (H2O2) in the atmosphere of Mars for the first time. This is the first time that a chemical catalyst of this sort has been found in a planetary atmosphere other than the Earth’s. Catalysts control the reactions of the most important chemical cycles in the Earth’s atmosphere. The result shows that scientists’ knowledge of the Earth’s atmosphere can be used to explain the chemistry of atmospheres on other planets, and vice versa. The work is announced in the March issue of the journal “Icarus”. The observations were made at the James Clerk Maxwell Telescope (JCMT), situated near the 14000-ft summit of Mauna Kea in Hawaii.

Dr Todd Clancy, at the Space Science Institute (SSI) in Boulder, Colorado, led the research team. He says “Mars is one of three observable terrestrial atmospheres. Unlike Venus, Mars is hospitable enough to be considered a possible human habitat in the future. And unlike the Earth, Mars is not extensively explored and so presents an opportunity to discover new and exciting phenomena.”

Dr Brad Sandor, also at SSI, explains “We took advantage of the excellent 2003 opposition of Mars, when the Earth and Mars passed close by each other in their orbits around the sun, to measure Martian atmospheric H2O2 for the first time.”

The Earth’s atmosphere has been studied much more than that of Mars. Scientists have had to rely on their terrestrial experience to guess how the Martian atmosphere reacts to solar radiation, and how its overall photochemical balance is controlled.

Models predicted that hydrogen peroxide was the key catalytic chemical that controls Mars atmospheric chemistry. Until now, scientists were unable to detect the predicted amount of H2O2, so some researchers argued that the models were wrong.

However, the new measurements of hydrogen peroxide made with the JCMT agree with the predictions of standard photochemistry. Dr Clancy continues “We have largely confirmed that the chemical balance of the Mars atmosphere is determined by the products of the photolysis of water vapor, without the need for special or unknown changes to current theory.”

Dr Gerald Moriarty-Schieven of the National Research Council of Canada worked on the project with Dr Clancy and Dr Sandor, and is based at the Joint Astronomy Centre in Hawaii, which operates the JCMT. He explains more about the JCMT observations: “The 2003 opposition was especially favorable since it occurred when Mars was closest to the sun in its orbit, and hence unusually close to us as we passed by. Mars was at its warmest, when the most H2O2 is available to observe, and the JCMT can make especially sensitive H2O2 measurements.”

What impact does this result have for the search for life on Mars? Dr Clancy says “Hydrogen peroxide is actually used as an antiseptic here on Earth, and so it would tend to retard any biological activity on the surface on Mars. For this reason, as well as the ultraviolet radiation and lack of water, bacteria-like organisms are not expected to be viable on the surface. Most arguments for finding life on Mars now center on subsurface regions.”

Original Source: JACH News Release

Image credit: ESA
The colour image (with north at the top) shows the summit caldera of Hecates Tholus, the northernmost volcano of the Elysium volcano group. The volcano reveals multiple caldera collapses. On the flanks of Hecates Tholus, several flow features related to water (lines radiating outwards) and pit chains related to lava can be observed. The volcano has an elevation of 5300 m, the caldera has a diameter of maximum 10 km and a depth of 600 m. The image centre is located at 150? East and 31.7? North.

Credits: ESA/DLR/FU Berlin (G. Neukum)

Original Source: ESA News Release

Image credit: NASA/JPL
Dust gradually obscures the Sun during a blue-sky martian sunset seen in a sequence of newly processed frames from NASA’s Mars Exploration Rover Opportunity.

“It’s inspirational and beautiful, but there’s good science in there, too,” said Dr. Jim Bell of Cornell University, Ithaca, N.Y., lead scientist for the panoramic cameras on Opportunity and its twin, Spirit.

The amount of dust indicated by Opportunity’s observations of the Sun is about twice as much as NASA’s Mars Pathfinder lander saw in 1997 from another site on Mars.

The sunset clip uses several of the more than 11,000 raw images that have been received so far from the 18 cameras on the two Mars Exploration Rovers and publicly posted at http://marsrovers.jpl.nasa.gov. During a briefing today at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., Bell showed some pictures that combine information from multiple raw frames.

A patch of ground about half the area of a coffee table, imaged with the range of filters available on Opportunity’s panoramic camera, has soil particles with a wide assortment of hues — “more spectral color diversity than we’ve seen in almost any other data set on Mars,” Bell said.

Opportunity is partway through several days of detailed observations and composition measurements at a portion of the rock outcrop in the crater where it landed last month. It used its rock abrasion tool this week for the first time, exposing a fresh rock surface for examination. That surface will be studied with its alpha particle X-ray spectrometer for identifying chemical elements and with its Moessbauer spectrometer for identifying iron-bearing minerals. With that rock-grinding session, all the tools have now been used on both rovers.

Dr. Ray Arvidson of Washington University, St. Louis, deputy principal investigator for the rovers’ science work, predicted that in two weeks or so, Opportunity will finish observations in its landing-site crater and be ready to move out to the surrounding flatland. At about that same time, Spirit may reach the rim of a larger crater nicknamed “Bonneville” and send back pictures of what’s inside. “We’ll both be at the rims of craters,” he said of the two rovers’ science teams, “one thinking about going in and the other thinking about going out onto the plain.”

Not counting occasional backup moves, Spirit has driven 171 meters (561 feet) from its lander. It has about half that distance still to go before reaching the crater rim. The terrain ahead looks different than what’s behind, however. “It’s rockier, but we’re after rocks,” Arvidson said.

Spirit can traverse the rockier type of ground in front of it, said Spirit Mission Manager Jennifer Harris of JPL. As it approached the edge of a small depression in the ground earlier this week, the rover identified the slope as a potential hazard, and “did the right thing” by stopping and seeking an alternate route, she said.

However, engineers are also planning to transmit new software to both rovers in a few weeks to improve onboard navigation capabilities. “We want to be more robust for the terrain we’re seeing,” Trosper said. The software revisions will also allow engineers to turn off a heater in Opportunity’s arm, which has been wasting some power by going on during cold hours even when not needed.

As it heads toward “Bonneville” to look for older rocks from beneath the region’s current surface layer, Spirit is stopping frequently to examine soil and rocks along the way. Observations with its microscope at one wavy patch of windblown soil allowed scientists to study how martian winds affect the landscape. Coarser grains are concentrated on the crests, with finer grains more dominant in the troughs, a characteristic of “ripples” rather than of dunes, which are shaped by stronger winds. “This gives us a better understanding of the current erosion process due to winds on Mars,” said Shane Thompson, a science team collaborator from Arizona State University, Tempe.

The rovers’ main task is to explore their landing sites for evidence in the rocks and soil about whether the sites’ past environments were ever watery and possibly suitable for sustaining life.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Image credit: NASA/JPL
On sol 32, which ended at 4:15 a.m. Thursday, February 26, Opportunity awoke to “Let It Be” by the Beatles. Opportunity’s day was focused on getting a second Moessbauer instrument measurement of the hole created by the rock abrasion tool at the “McKittrick” rock site. The Moessbauer can detect spectral signatures of different iron-bearing minerals.

The data from the first Moessbauer spectrum of “McKittrick” was received on Earth Wednesday afternoon. The alpha proton X-ray spectrometer data from yestersol at this target was retransmitted to Earth again Wednesday to get missing packets of data that were not received during the first data communications relay. Opportunity also snapped pictures of the rock areas named “Maya” and “Jericho” with the panoramic camera and took miniature thermal emission spectrometer measurements of the sky and “El Capitan” throughout the sol.

The amount of power Opportunity is able to generate continues to dwindle due to the decreasing amount of sunlight (energy) reaching the solar panels during the martian seasonal transition to winter. Because of this, the engineers are adjusting the rover?s daily communications activities. To minimize power use for communications sessions, engineers began a new “receive only” morning direct-from-earth communication relay. This lower-power communication mode was successful. Opportunity will continue with this approach to maximize the available power for driving and science activities as Mars moves farther away from Earth and the Sun in its elliptical orbit.

In conjunction with the morning communications session change, engineers added a second afternoon Mars Odyssey orbiter relay pass, which uses less power in transmitting data volume than direct-to-Earth communication. This additional Odyssey pass more than compensated for the elimination of the morning direct-to-Earth downlink. Engineers also continue to effectively use rover “naps” throughout the day to maximize energy savings.

The plan for sol 33, which ends at 4:55 a.m. Friday, February 27, is to take a very short trip (10 to 20 centimeters or 4 to 8 inches) towards the next rock abrasion tool target site, “Guadalupe.”

Original Source: NASA/JPL Status Report

Image credit: NASA/JPL
On sol 31, which ended at 3:36 a.m. Wednesday, February 25, Opportunity awoke to “Rock Around the Clock” by Bill Haley and his Comets. At 1:00 a.m. Local Solar Time, Opportunity sent data to Earth via the Mars Global Surveyor orbiter and then sent another whopping 145.6 megabits of data at 3:30 a.m. Local Solar Time via the Mars Odyssey orbiter.

During the morning hours, Opportunity collected data with the alpha particle X-ray spectrometer for five hours and took measurements with its miniature thermal emission spectrometer from inside its newly formed hole that was created on sol 30 by the rock abrasion tool. Later, Opportunity retracted and closed the door of the alpha particle X-ray spectrometer and swapped the Moessbauer spectrometer into the hole made by the abrasion tool for a leisurely 24-hour observation.

Opportunity also updated its “attitude knowledge,” which fine-tunes the rover’s information about its exact location and position on Mars. Updating the attitude knowledge allows the rover to more accurately point the high gain antenna toward Earth, which increases the communications capabilities. The attitude adjustment also enables scientists and engineers to point instruments onboard Opportunity more precisely at targets of interest, such as particular rocks and patches of soil. To adjust the attitude knowledge, engineers have the rover turn the panoramic camera to the Sun and watch the Sun travel across the sky for 15 minutes. The rover is then smart enough to take the Sun movement data collected from the panoramic camera to calculate its own location in the universe?..on Mars. The rover gathers attitude knowledge errors over time as it drives and uses the robotic arm extensively, but it only needs an attitude adjustment about once a week or after driving long distances.

Around 12:15 pm Local Solar Time, Opportunity went to sleep to recharge its batteries from its strenuous rock abrasion tool activities on sol 30, but reawakened briefly at 4 p.m. Local Solar Time and again in the evening to send data to Earth via additional overflights by the Mars Global Surveyor and Odyssey orbiters.

The plan for sol 32, which ends at 4:15 a.m. Thursday, February 26, is to take another unique set of Moessbauer measurements to look at the rover-created hole in a different spectrum. The goal is to then crawl slightly forward on sol 33 to position Opportunity to use the rock abrasion tool on the upper target of the El Capitan/McKittrick area.

Original Source: NASA/JPL News Release

Image credit: NASA
Confused? Then you’re just like plants in a greenhouse on Mars.

No greenhouses exist there yet, of course. But long-term explorers, on Mars, or the moon, will need to grow plants: for food, for recycling, for replenishing the air. And plants aren’t going to understand that off-earth environment at all. It’s not what they evolved for, and it’s not what they’re expecting.

But in some ways, it turns out, they’re probably going to like it better! Some parts of it, anyway.

“When you get to the idea of growing plants on the moon, or on Mars,” explains molecular biologist Rob Ferl, director of Space Agriculture Biotechnology Research and Education at the University of Florida, “then you have to consider the idea of growing plants in as reduced an atmospheric pressure as possible.”

There are two reasons. First, it’ll help reduce the weight of the supplies that need to be lifted off the earth. Even air has mass.

Second, Martian and lunar greenhouses must hold up in places where the atmospheric pressures are, at best, less than one percent of Earth-normal. Those greenhouses will be easier to construct and operate if their interior pressure is also very low — perhaps only one-sixteenth of Earth normal.

The problem is, in such extreme low pressures, plants have to work hard to survive. “Remember, plants have no evolutionary preadaption to hypobaria,” says Ferl. There’s no reason for them to have learned to interpret the biochemical signals induced by low pressure. And, in fact, they don’t. They misinterpret them.

Low pressure makes plants act as if they’re drying out.

In recent experiments, supported by NASA’s Office of Biological and Physical research, Ferl’s group exposed young growing plants to pressures of one-tenth Earth normal for about twenty-four hours. In such a low-pressure environment, water is pulled out through the leaves very quickly, and so extra water is needed to replenish it.

But, says Ferl, the plants were given all the water they needed. Even the relative humidity was kept at nearly 100 percent. Nevertheless, the plants’ genes that sensed drought were still being activated. Apparently, says Ferl, the plants interpreted the accelerated water movement as drought stress, even though there was no drought at all.

That’s bad. Plants are wasting their resources if they expend them trying to deal with a problem that isn’t even there. For example, they might close up their stomata — the tiny holes in their leaves from which water escapes. Or they might drop their leaves altogether. But, those responses aren’t necessarily appropriate.

Fortunately, once the plants’ responses are understood, researchers can adjust them. “We can make biochemical alterations that change the level of hormones,” says Ferl. “We can increase or decrease them to affect the plants’ response to its environment.”

And, intriguingly, studies have found benefits to a low pressure environment. The mechanism is essentially the same as the one that causes the problems, explains Ferl. In low pressure, not only water, but also plant hormones are flushed from the plant more quickly. So a hormone, for example, that causes plants to die of old age might move through the organism before it takes effect.

Astronauts aren’t the only ones who will benefit from this research. By controlling air pressure, in, say, an Earth greenhouse or a storage bin, it may be possible to influence certain plant behaviors. For example, if you store fruit at low pressure, it lasts much longer. That’s because of the swift elimination of the hormone ethylene, which causes fruit to ripen, and then rot. Farm produce trucked from one coast to the other in low pressure containers might arrive at supermarkets as fresh as if it had been picked that day.

Much work remains to be done. Ferl’s team looked at the way plants react to a short period of low pressure. Still to be determined is how plants react to spending longer amounts of time — like their entire life — in hypobaric conditions. Ferl also hopes to examine plants at a wider variety of pressures. There are whole suites of genes that are activated at different pressures, he says, and this suggests a surprisingly complex response to low pressure environments.

To learn more about this genetic response, Ferl’s group are bioengineering plants whose genes glow green when activated. In addition they are using DNA microchip technology to examine as many as twenty-thousand genes at a time in plants exposed to low pressures.

Plants will play an extraordinarily important role in allowing humans to explore destinations like Mars and the Moon. They’ll will provide food, oxygen and even good cheer to astronauts far from home. To make the best use of plants off-Earth, “we have to understand the limits for growing them at low pressure,” says Ferl. “And then we have to understand why those limits exist.”

Ferl’s group is making progress. “The exciting part of this is, we’re beginning to understand what it will take to really use plants in our life support systems.” When the time comes to visit Mars, plants in the greenhouse might not be so confused after all.

Original Source: NASA Science News

Image credit: NASA/JPL
Opportunity has been getting the lion’s share of the attention in recent weeks, because its twin sister Spirit has been engaged mostly in long-distance driving. But it may be about to steal the spotlight. For several sols, Spirit has been working its way towards nearby Bonneville crater. But even before it gets there, the mobile robot may make a critical discovery. It may find evidence of liquid water on Mars.

Well, not exactly liquid water. Liquid brine, actually. Brine is water that contains dissolved salts. The salts lower the melting temperature of the mixture so that it remains liquid well below the freezing point of pure water. (That’s why road crews “salt” roadways to melt ice in the winter.) Scientists have long speculated that brines, or super brines – a super brine contains high concentrations of dissolved salts – may exist in the martian subsurface.

Spirit’s discovery of patterns in the surface soil at Gusev Crater is what led scientists to believe that there may be subsurface brines there. As of sol 45 (Tuesday, February 17), Spirit had traveled to Laguna Hollow, a small depression located about halfway between Spirit’s landing site and Bonneville crater. In the fine-grained surface material inside the hollow, scientists can see irregular patterns of lines and polygons.

The science team is anxious to learn more about this material, which is unlike anything seen before on Mars. They saw that the topmost layer appeared to be made of different material than what lay just beneath it, and that the surface material stuck to the rover’s wheels.

Dave Des Marais, a science team member from NASA Ames Research Center, explained the possibilities this way: “It could be that it’s a very fine grained dust; fine dust can be coherent when it’s compressed. But it could also have salt in it, or for that matter, a brine or a little bit of water to give it moisture.” On Earth, he said, “you can get that with freeze-thaw type activity, at higher latitudes, such as in tundra. You can also get that in a salt flat, where the salt, by warming, or by wetting and drying, expands and contracts, and forms a very characteristic polygon pattern. You can do it with mud flats, with mud cracks.”

Next on the agenda for Spirit is to dig a deeper trench into the Laguna Hollow material. That, said Des Marais, will enable the MER science team to determine why the material is sticky. “If we’re looking at salt that’s moving up and down, with the assistance of water, we might expect to see a concentration of salt near the surface and as we go deeper perhaps less of a concentration.”

Because the patterns are visible at the surface, Des Marais speculates that they could be due to an active, ongoing process on Mars. Even if the process is currently active, though, that doesn’t necessarily mean there’s a sub-surface body of water present. “I wouldn’t expect to see a pool of water when we dig. You don’t need to have that much [water] to explain these properties that we see. It could be just enough to cause a moistening and a very dense concentrated brine,” he said.

If there is brine beneath the surface at Laguna Hollow, the implications for the possibility of life on Mars could be tremendous. On Earth, some microbes have adapted to thrive in water containing concentrations of salts many times that of sea water. Microbes have also been found eking out a meager existence in tiny brine pockets scattered throughout Arctic sea ice. Scientists know for certain that these microbes can survive at temperatures as low as minus 20 degrees Celsius (minus 4 degrees Fahrenheit). It’s possible that they can live at even lower temperatures.

Meanwhile, Opportunity has completed its first trenching operation into the soil at the floor of the crater where it landed. It will now move on to conduct a more detailed exploration of “El Capitan,” the name that has been given to a portion of the nearby bedrock outcrop. El Capitan offers the most extensive stratigraphic section (the tallest continuous stack of exposed layers, or strata) in the outcrop. The topmost layers appear to be composed of different material than the lower layers. By examining both regions in detail, scientists hope to gain a better understanding of the origin of both the rock matrix (the material the layers are composed of) and the tiny spherules that are embedded within the matrix.

One particularly intriguing discovery at Meridiani is the presence of sulfur on the surface of the bedrock. How the sulfur got there is still unknown. Scientists want to find out whether it is present merely within a surface coating, or deeper within the rock. “If we see it only at the surface and not below the surface,” said Steve Squyres, principle investigator for the MER mission, “then it’s some kind of coating.” That, he said, would “tell us something interesting about recent processes, but it doesn’t tell us about the formation of the outcrop itself.”

If, on the other hand, Opportunity ground into the rock with its RAT and detected sulfur deeper within the rock, it would indicate that the sulfur was around long ago, when the bedrock formed. Scientists would then want to know which sulfate (sulfur-containing) minerals were present within the rock. There are many different types of sulfate minterals. Some form in volcanic environments; many others, such as gypsum, form in the presence of water.

According to Squyres, if the M?ssbauer spectrometer detects “evidence for a sulfate that is the kind that forms only in the presence of liquid water, that would be an extraordinarily exciting finding. That would be probably the most interesting thing that we’d found yet” at Meridiani.

Original Source: Astrobiology Magazine