NASA's Mars Odyssey spacecraft has successfully adjusted its orbital location to be in a better position to provide prompt confirmation of the August landing of the Curiosity rover at the Gale Crater site.
NASA's Mars Science Laboratory spacecraft carrying Curiosity can send limited information directly to Earth as it enters Mars' atmosphere. Before the landing, Earth will set below the Martian horizon from the descending spacecraft's perspective, ending that direct route of communication. Odyssey will help to speed up the indirect communication process.
A spacecraft thruster burn Tuesday, July 24, lasting about six seconds has nudged Odyssey about six minutes ahead in its orbit. Odyssey is now operating normally, and confirmation of Curiosity's landing is expected to reach Earth at about 10:31 p.m. PDT on Aug. 5 (early Aug. 6, EDT and Universal Time), as originally planned.
"Information we are receiving indicates the maneuver has completed as planned," said Mars Odyssey Project Manager Gaylon McSmith of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Odyssey has been working at Mars longer than any other spacecraft, so it is appropriate that it has a special role in supporting the newest arrival."
Two other Mars orbiters, NASA's Mars Reconnaissance Orbiter and the European Space Agency's Mars Express, also will be in position to receive radio transmissions from the Mars Science Laboratory during its descent. However, they will be recording information for later playback, not relaying it immediately, as only Odyssey can.
The graphic below shows key features at the MSL landing site in Gale crater. A possible traverse path is shown in orange. Branching valleys from the crater wall lead to an alluvial fan in the center of the ellipse. At the end of the alluvial fan, the terrain transitions to a fractured, layered unit with a high thermal inertia. Several fresh craters in this unit are accessible.
Because of its history, 96-mile wide Gale Crater crater landing site, with its strangely sculpted mountain --three times higher than the Grand Canyon is deep--is the ideal place for Curiosity to conduct its mission of exploration into the Red Planet's past. Researchers plan to use Curiosity to study layers in the mountain that hold evidence about wet environments of early Mars.
"This may be one of the thickest exposed sections of layered sedimentary rocks in the solar system," said Joy Crisp, MSL Deputy Project Scientist from NASA's Jet Propulsion Laboratory. "The rock record preserved in those layers holds stories that are billions of years old -- stories about whether, when, and for how long Mars might have been habitable."
An instrument on Curiosity can check for any water that might be bound into shallow underground minerals along the rover's path. Today the Red Planet is a radiation-drenched, bitterly cold, bleak world. Enormous dust storms explode across the barren landscape and darken Martian skies for months at a time. But data from the Mars Reconnaissance Orbiter suggest that Mars once hosted vast lakes and flowing rivers.
While simple molecules could provide evidence of ancient Martian life, they could also stem from other sources like meteorites and volcanoes. Complex organic molecules could hint more strongly at the possibility of past life on the planet. These molecules, made up of 10 or more carbon atoms, could resemble known building blocks of life such as the amino acids that make up proteins.
Although complex carbon structures are trickier to find because they're more vulnerable to cosmic radiation that continuously bombards and penetrates the surface of the Red Planet, research by Pavlov and his colleagues provides suggestions for where to start looking. The amounts of radiation that rock and soil is exposed to over time, and how deep that radiation penetrates – an indicator of how deep a rover would have to sample to find intact organic molecules – is a subject of ongoing research.
The scientists report that chances of finding these molecules in the first 2 centimeters (0.8 inches) of Martian soil is close to zero. That top layer, they calculate, will absorb a total of 500 million grays of cosmic radiation over the course of one billion years – capable of destroying all organic material. A mere 50 grays, absorbed immediately or over time, would cause almost certain death to a human.
However, within 5 to 10 centimeters (2 to 4 inches) beneath the surface, the amount of radiation reduces tenfold, to 50 million grays. Although that's still extreme, the team reports that simple organic molecules, such as a single formaldehyde molecule, could exist at this depth – and in some places, specifically young craters, the complex building blocks of life could remain as well.
"Right now the challenge is that past Martian landers haven't seen any organic material whatsoever," according to AlexanderPavolov of NASA's GoddardSpace FlightCenter. "We know that organic molecules have to be there but we can't find any of them in the soil."
As Mars revolves around the Sun, it is constantly bombarded by very small meteors and interplanetary dust particles, which have plenty of organic compounds in them, Pavlov said. Therefore, over time they would have accumulated at the Martian surface.
The Mars Science Laboratory is the newest and largest of NASA's Martian landers and is scheduled to touch down August 2012. Curiosity doesn't have a shovel but, equipped with drilling technology, it will collect, store, and analyze samples of Martian material down to 5 centimeters below the surface of rock and soil. Past Martian rovers have only collected loose soil atop the surface that has been directly exposed to cosmic radiation, making the possibility for detecting organic molecules exceedingly slim.
When evaluating how deep organic molecules might persist beneath the surface, previous studies have mainly focused on the maximum depth, approximately 1.5 meters (5 feet), that cosmic radiation reaches because beyond that point organic molecules could survive, unharmed, for billions of years, Pavlov said. However, drilling to 1.5 meters or deeper is currently too expensive to engineer for a Martian rover.
So the NASA team has focused on more attainable depths – the first 20 cm (8 in) below the surface. They modeled the complex scenario of cosmic ray accumulation and its effects on organic molecules using a collection of important variables, including Martian rock and soil composition, changes in the planet's atmospheric density over time, and cosmic rays' various energy levels.
In addition to the finding that some simple carbon-containing molecules could exist within 10 cm (4 in) depth, the scientists emphasize that certain regions on Mars may have radiation levels far lower than 50 million grays near the surface – and so more complex molecules like amino acids could remain intact.
In order to find these molecules within the rover's drilling range (1 to 5 cm), the scientists found the best bet is to look at "fresh" craters that are no more than 10 million years old, unlike past expeditionary sites that mainly sampled from landscapes undisturbed for billions of years.
Compared to Martian landscapes undisturbed for one billion years or more, relatively young craters exhibit freshly exposed rock and soil that was once deeper beneath the surface. The new research indicates that this material will have been near the surface for a short enough period of time that it's overall exposure to harmful radiation would not have been enough to wipe out organic molecules.
"When you have a chance to drill, don't waste it on perfectly preserved (landscapes)," Pavlov said. "You want to go to fresh craters because there's probably a better chance to detect complex organic molecules. Let Nature work for you."
The Daily Galaxy via NASA Curiosity Mission
Image credit: Wikipedia Commons