Universe Today

Peas growing onboard the International Space Station. Image credit: The crew of ISS Expedition 6, NASA. Click to enlarge
Anxiety can be a good thing. It alerts you that something may be wrong, that danger may be close. It helps initiate signals that get you ready to act. But, while an occasional bit of anxiety can save your life, constant anxiety causes great harm. The hormones that yank your body to high alert also damage your brain, your immune system and more if they flood through your body all the time.

Plants don’t get anxious in the same way that humans do. But they do suffer from stress, and they deal with it in much the same way. They produce a chemical signal — superoxide (O2-) — that puts the rest of the plant on high alert. Superoxide, however, is toxic; too much of it will end up harming the plant.

This could be a problem for plants on Mars.

According to the Vision for Space Exploration, humans will visit and explore Mars in the decades ahead. Inevitably, they’ll want to take plants with them. Plants provide food, oxygen, companionship and a patch of green far from home.

On Mars, plants would have to tolerate conditions that usually cause them a great deal of stress — severe cold, drought, low air pressure, soils that they didn’t evolve for. But plant physiologist Wendy Boss and microbiologist Amy Grunden of North Carolina State University believe they can develop plants that can live in these conditions. Their work is supported by the NASA Institute for Advanced Concepts.

Stress management is key: Oddly, there are already Earth creatures that thrive in Mars-like conditions. They’re not plants, though. They’re some of Earth’s earliest life forms–ancient microbes that live at the bottom of the ocean, or deep within Arctic ice. Boss and Grunden hope to produce Mars-friendly plants by borrowing genes from these extreme-loving microbes. And the first genes they’re taking are those that will strengthen the plants’ ability to deal with stress.

Ordinary plants already possess a way to detoxify superoxide, but the researchers believe that a microbe known as Pyrococcus furiosus uses one that may work better. P. furiosus lives in a superheated vent at the bottom of the ocean, but periodically it gets spewed out into cold sea water. So, unlike the detoxification pathways in plants, the ones in P. furiosus function over an astonishing 100+ degree Celsius range in temperature. That’s a swing that could match what plants experience in a greenhouse on Mars.

The researchers have already introduced a P. furiosus gene into a small, fast-growing plant known as arabidopsis. “We have our first little seedlings,” says Boss. “We’ll grow them up and collect seeds to produce a second and then a third generation.” In about one and a half to two years, they hope to have plants that each have two copies of the new genes. At that point they’ll be able to study how the genes perform: whether they produce functional enzymes, whether they do indeed help the plant survive, or whether they hurt it in some way, instead.

Eventually, they hope to pluck genes from other extremophile microbes — genes that will enable the plants to withstand drought, cold, low air pressure, and so on.

The goal, of course, is not to develop plants that can merely survive Martian conditions. To be truly useful, the plants will need to thrive: to produce crops, to recycle wastes, and so on. “What you want in a greenhouse on Mars,” says Boss, “is something that will grow and be robust in a marginal environment.”

In stressful conditions, notes Grunden, plants often partially shut down. They stop growing and reproducing, and instead focus their efforts on staying alive–and nothing more. By inserting microbial genes into the plants, Boss and Grunden hope to change that.

“By using genes from other sources,” explains Grunden, “you’re tricking the plant, because it can’t regulate those genes the way it would regulate its own. We’re hoping to [short-circuit] the plant’s ability to shut down its own metabolism in response to stress.”

If Boss and Grunden are successful, their work could make a huge difference to humans living in marginal environments here on Earth. In many third-world countries, says Boss, “extending the crop a week or two when the drought comes could give you the final harvest you need to last through winter. If we could increase drought resistance, or cold tolerance, and extend the growing season, that could make a big difference in the lives of a lot of people.”

Their project is a long-term one, emphasize the scientists. “It’ll be a year and a half before we actually have [the first gene] in a plant that we can test,” points out Grunden. It’ll be even longer before there’s a cold- and drought-loving tomato plant on Mars–or even in North Dakota. But Grunden and Boss remain convinced they will succeed.

“There’s a treasure trove of extremophiles out there,” says Grunden. “So if one doesn’t work, you can just go on to the next organism that produces a slightly different variant of what you want.”

“Amy’s right,” agrees Boss. “It is a treasure trove. And it’s just so exciting.”

Original Source: NASA News Release

Perspective view of Reull Vallis. Image credit: ESA Click to enlarge
The Mars Reconnaissance Orbiter, set to launch on August 10, will search for evidence that liquid water once persisted on the surface of Mars. This orbiter also will provide detailed surveys of the planet, identifying any obstacles that could jeopardize the safety of future landers and rovers.

Jim Graf, Project Manager for the Mars Reconnaissance Orbiter, gave a talk where he provided an overview of the mission. In part one of this edited transcript, Graf discusses previous studies of Mars, and describes the steps that will put MRO in orbit around the Red Planet.

“In the 1900s, our knowledge of Mars was based on looking at albedo features, the bright and dark spots. And, guess what? They moved all over. We didn’t know about the dust storms that cover the planet, since all we could do was look at Mars through a telescope from afar. We also saw a lot of straight lines, and some people believed those lines were canals that brought water from the poles down to the arid regions. There were little green men running around in oases all over.

Fast-forward sixty-five years to when Mariner 4 came by, we saw a moon-like surface: craters, no real water, devoid of life, no Martians, no oases, no canals. At that particular point in time we said, ‘There’s nothing really there. Let’s go look elsewhere.’ But thankfully, future Mariners were in the queue and already had been approved for going to Mars to investigate it more thoroughly. When they arrived there, our image of Mars changed. We saw evidence that water once flowed on the surface. There were craters that had been partly subsumed, crater walls that were partly destroyed as if water flowed by. Other images showed almost delta-like regions, where water had been captured in one area and then came down in streams and gullies.

The wide angle view of the martian north polar cap was acquired on March 13, 1999, during early northern summer. The light-toned surfaces are residual water ice that remains through the summer season. The nearly circular band of dark material surrounding the cap consists mainly of sand dunes formed and shaped by wind. Credit: NASA/JPL/Malin Space Science Systems

We’ve had a lot of orbiters since the Mariner missions, and not only do we see water features in the land, but we also see evidence of tectonics, or possibly volcanic activity. Olympus Mons is the largest volcano in the solar system. Valles Marineris, named after the Mariner spacecraft that found it, is 4,000 kilometers wide, the same distance across as the United States, and it’s 6 kilometers deep. It has tributaries that dwarf our Grand Canyon. So the planet has started coming alive, not with Martians, but geologically.

The thermal emission spectrometer on Mars Global Surveyor told us about the minerals in the surface. We saw hematite in one particular area on the planet. If you look at this area through a regular telescope there is nothing to suggest that there was once water there. But if you look at it through a spectrometer, you can see the minerals and say, ‘There’s hematite there. On Earth, hematite is generally created at the base of lakes and rivers. So, what made that hematite on Mars?’

We decided to send the Opportunity rover there. It landed in Eagle Crater, which is about 20 meters in diameter and has a very flat surface. There are little nodules called ‘blueberries’ on this surface, and these nodules contained the hematite that was seen from orbit. After months of intense investigation with the rover, we think there was standing water in this area that created the hematite.

The rover is investigating an area that’s only about a kilometer or two in area – that’s all it can rove and see. So you’ve got to ask yourself, ‘Is the rest of the planet like this?’ And the answer is no. The Spirit rover landed on the other side of the planet, in Gusev Crater, and it’s very different geologically from where Opportunity landed.

It’s wonderful to have two intensive investigations on opposite sides of the planet. But there’s a lot more to the planet than just those two sites. From orbit, these sites are just pinpricks.

Mars is a dynamic planet, and we really need the yin and the yang of a lander and orbiter to understand it. A lander goes down and intensively investigates a particular area, and then orbiters take that basic knowledge and apply it to the entire globe.

The Mars Reconnaissance Orbiter — affectionately known as MRO, or Mister O — will take that basic knowledge we have from the landers, and use the most advanced instruments that we can develop to investigate the entire planet. We want to characterize the present climate on Mars, and to look for changes in that climate. We want to study complex, layered terrain, and understand why it came about. And, most of all, we want to find evidence of water. On Earth, wherever you have water, plus the basic nutrients and energy, you will find life. So if we find liquid water on Mars, we may also find life there, or life that was there at one time. So one of our objectives for MRO is to follow the water.

When you only have two landers in a decade, you want to put them down in some place on that vast planet where you know you’re going to get the maximum science. That’s what we did with Opportunity, sending it to where we saw hematite from orbit. We have two more landers coming up: one in ’07 and one in ’09. Where are we going to land those? MRO will provide information on composition, which will tell you where you want to go scientifically, and it will provide detailed imaging, which will tell you where you can go safely.

Once the landers are down on the surface, we have to get the data from them back to Earth. MRO will provide a basic fundamental link for those landers, so they can send an immense amount of data back, taking full advantage of the huge telecommunications system that we have onboard the spacecraft.

There are five phases to the MRO mission. We like to think of it as MRO’s five easy pieces. We say that ironically, because none of these are easy.

The first one is the launch. I think of it as a wedding. You spend years and years getting ready for it and it’s over in a few hours, and it better go right or else you’re never going to be able to recover.

Then we have a cruise phase, where we leave Earth orbit and head to Mars. It takes about seven months to get there.

Third, we have the approach and orbit insertion. This is where we’ll have so much energy that we’d fly right by the planet. We’ll have to fire our thrusters to slow ourselves down so gravity can catch us and bring us into orbit. It’s white-knuckle time.

After that, we get into what we consider to be the most dangerous phase: the aerobraking. We dip into the atmosphere a little bit at a time, taking energy out of the orbit.

Finally, we get to the gravy. We turn the science instruments on and we get two Earth years worth of science, plus two more years worth of relay support, with the main mission ending in December of 2010.

So let’s go back and talk about each phase. First, we’ll be launched August 10, 2005 at 8:00 in the morning Eastern Time, on an Atlas V-401 rocket. This type of vehicle has flown twice before and our particular vehicle, oddly enough, has a serial number of 007. I like to think of it as License to Recon.’

It has two stages. The first stage uses RD-180 engines that come from Russia, and it will launch us on our way. Eventually it will burn out and we will separate the first and second stage, go through a coast period, fire the second stage – we actually fire it twice, and the second time is a long burn – and that puts us on our cruise phase.

Once we’re in orbit, we deploy our solar arrays and our high-gain antenna, which is used for communicating back to Earth. This is when all the major deployments are done. This is different from other missions that had to do additional major deployments once they got to Mars.

When we approach Mars, we will go under the south pole. As we start coming up on the other side, we will fire our main engines. We have six engines, and each puts out 170 Newtons of thrust, so we have over 900 Newtons that will be fired. We will fire our hydrazine thrusters for about 30 minutes. Then we go behind the planet, and we will not have any telemetry at that particular point in time until the burn is completed and the spacecraft emerges from behind Mars.

When that happens, we will be in a very elliptical orbit. Our orbit will extend out from the planet at the furthest point – apoapsis – about 35,000 kilometers and we will be about 200 kilometers at the closest point. This sets up the next phase, the aerobraking.

In aerobraking, we will use the backs of the solar arrays, the body of the spacecraft, and the back of the high-gain antennae to create drag, slowing us down as it goes through the atmosphere. So, every time we are close to the planet, we will dip through the atmosphere and slow ourselves down. Now the way orbital mechanics work, if you take energy out through drag, you bring the apoapsis down. So over about a seven to eight month period, we will dip into the planet’s atmosphere 514 times, slowly bringing our orbit down to our final science orbit.

Then we get into the gravy of doing the science. Removing the covers off our instruments are the last minor deployments that we have to do, and then we start acquiring data. We can acquire data over the entire planet — the mountains, the valleys, the poles — for two years.”

Original Source: NASA Astrobiology

Artist’s impression of MARSIS deployment complete. Image credit: ESA Click to enlarge
MARSIS, the sounding radar on board ESA?s Mars Express spacecraft, is collecting the first data about the surface and the ionosphere of Mars.

The radar started its science operations on 4 July 2005, after the first phase of its commissioning was concluded on the same day. Due to the late deployment of MARSIS, it was decided to split the commissioning, originally planned to last four weeks, into two phases, one of which has just ended and the second one to be started by December this year.

This has given the instrument the chance to start scientific observations earlier than initially foreseen, while still in the Martian night. This is the environmental condition favourable to subsurface sounding, because the ionosphere is more ?energised? during the daytime and disturbs the radio signals used for subsurface observations.

From the beginning of the commissioning, the two 20-metre long antenna booms have been sending radio signals towards the Martian surface and receiving echoes back. ?The commissioning phase confirmed that the radar is working very well, and that it can be operated at full power without interfering with any of the spacecraft systems,? says Roberto Seu, Instrument Manager for MARSIS, from the University of Rome ?La Sapienza?, Italy.

MARSIS is a very complex instrument, capable of operating at different frequency bands. Lower frequencies are best suited to probe the subsurface and the highest frequencies are used to probe shallow subsurface depths, while all frequencies are suited to study the surface and the upper atmospheric layer of Mars.

?During the commissioning we have worked to test all transmission modes and optimise the radar performance around Mars,? says Prof. Giovanni Picardi, Principal Investigator for MARSIS, University of Rome ?La Sapienza?. ?The result is that since we have started the scientific observations in early July, we are receiving very clean surface echoes back, and first indication about the ionosphere.?

The MARSIS radar is designed to operate around the orbit ?pericentre?, when the spacecraft is closer to the planet?s surface. In each orbit, the radar has been switched on for 36 minutes around this point, dedicating the central 26 minutes to subsurface observations and the first and last five minutes of the slot to active ionosphere sounding.

Using the lower frequencies, MARSIS has been mainly investigating on the northern flat areas between 30? and 70? latitudes, at all longitudes. ?We are very satisfied about the way the radar is performing. In fact, the surface measurements taken so far match almost perfectly with the existing models of the Mars topography,? said Prof. Picardi. Thus, these measurements provided an excellent test.

The scientific reason to concentrate the first data analysis on flat regions lies in the fact that the subsurface layers here are in principle easier to identify, but the question is still tricky. ?As the radar is appearing to work so well for the surface, we have good reasons to think that the radio waves are correctly propagating also below the surface,? added Prof. Picardi.

?The biggest part of our work just started, as we now have to be sure that we clearly identify and isolate those echoes that come from the subsurface. To do this, we have to carefully screen all data and make sure that signals that could be interpreted as coming from different underground layers are not actually produced by surface irregularities. This will keep us occupied for a few more weeks at least.?

The first ionospheric measurements performed by MARSIS have also revealed some interesting preliminary findings. The radar responds directly to the number of charged particles composing the ionosphere (plasma). This has shown to be higher than expected at times.

?We are now analysing the data to find out if such measurements may result from sudden increases of solar activity, like the one observed on 14 July, or if we have to make new hypotheses. Only further analysis of the data can tell us,? said Jeffrey Plaut, Co-Principal Investigator, from NASA Jet Propulsion Laboratory, Pasadena, USA.

MARSIS will continue send signals to hit the surface and penetrate the subsurface until the middle of August, when the nighttime portion of the observations will have almost ended. After that, observation priority will be given to other Mars Express instruments that are best suited to work during daytime, such as the HRSC camera and the OMEGA mapping spectrometer.

However, MARSIS will continue surface and ionospheric investigations during daytime, with the ionospheric sounding being reserved for more than 20% percent of all Mars Express orbits, in all possible Sun illumination conditions.

In December 2005, the Mars Express orbit pericentre will enter the nighttime again. By then, the pericentre will have moved closer to the South pole, allowing MARSIS to restart optimal probing of the subsurface, this time in the southern hemisphere.

Original Source: ESA Portal