Author: Fraser Cain

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