“The Earth Strain” –Have NASA Missions Contaminated Mars?

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Should Earth bacteria make it to the surface of Mars' Gale Crater -landing site of the Mars Curiosity rover (above), terrestrial organics could contaminate soil samples, giving experiments false positives of a second genesis on Mars. Even worse, should there be indigenous life on Mars, any accidental microbes from Earth could destroy microbial alien life.


During the preparation for the launch of NASA's Mars Science Laboratory (MSL) Curiosity on Nov. 26, a step in the "planetary protection" procedure wasn't adhered to. The procedure's key purpose is to make sure organic material from Earth doesn't get transferred accidentally to the Red Planet.

As reported by Space.com's Leonard David, MSL project developers decided not to send a set of drill bits — attached to the rover's exterior, ready to be used by the robotic arm's drill — through a final ultra-cleanliness step before launch.

This deviation in protocol wasn't communicated to NASA's planetary protection officer Cassie Conley until it was too late. "(MSL project developers) didn't submit the request for the deviation not to comply with their planetary protection plan until several months ago," she said.

The deviation was made by project managers as they considered the risk to be very low — the rover wouldn't be drilling anywhere near potentially life-harboring ice in Gale Crater, the region of Mars Curiosity will be exploring.

When the Apollo 11 astronauts splashed down in the Pacific they were immediately whisked off into quarantine, spending three weeks in a rather unglamorous steel shell for fear that they'd contracted lethal space-plagues.

NASA's Mars mission lends living credibility to a paper by Professor Cockell of the Open University that points out that the flow of life is more likely to be FROM the vast dirty ball teeming with billions of organisms TO the utterly dead space rocks.  Who could have guessed?

The idea is that hardy hitchhikers on our interplanetary probes could face alien ecosystems with "The Earth Strain", and they won't even have a rugged team of determined scientists to find a cure.  Never mind that anything capable of surviving extended exposure to cosmic rays would have to be King Hardcore of the microorganic kingdom.

Some in the science community be;lieve we may have already contaminated Mars. But Earth microbes trying to make it to Mars must survive sterilization in NASA's clean rooms, harsh cosmic rays during months of space travel, and the Red Planet's unforgiving surface environment. But any bacteria that successfully hitchhike aboard the wheels of NASA's Mars Science Laboratory mission in 2012 might manage to scratch out a brief existence on the martian surface.

The finding comes from a study that examined how the new high-tech landing technique of the Mars Science Laboratory (MSL) may affect the risk of contaminating Mars. The mission will use both a parachute and downward-firing thruster rockets to slow its descent so that its "sky crane" can lower the SUV-sized Curiosity rover onto the surface — a direct touchdown that may give microbes a brief chance to experience life on Mars. That translates into a higher risk of contamination when compared to some past Mars rover missions, said Andrew C. Schuerger, a microbiologist at the University of Florida and the Space Life Sciences Lab at NASA's Kennedy Space Center in Florida. But he added that microbes still face tough odds for surviving space travel and martian conditions.

"Although this paper suggests we could be transferring bacteria to martian surface, we don't know for certain yet," Schuerger said. "We could very well be losing most due to the exposure to vacuum in space, cosmic rays and hard radiation. Even if cells are present on a rover wheel at launch, they might be dead by the time they get to Mars."

Schuerger and his colleague, Krystal Kerney, wanted to find out whether the wheels of Mars rovers past and future could contaminate the martian surface. They ran two experiments simulating the contamination possibilities for MSL versus the Mars Pathfinder mission of 1997 and the Mars Exploration Rovers (MER) that landed on the red planet in 2004.

The Mars Pathfinder rover, called Sojourner, sat on a landing platform for 2 martian days before rolling onto the surface. The twin MER rovers, Spirit and Opportunity, sat on their landing platforms for 12 and 7 martian days, respectively. Each martian day is just a little over 24 hours.

In the recent study, researchers simulated a Mars rover sitting on a landing platform for 1, 3 and 6 hours while being exposed to martian levels of ultraviolet (UV) rays. Even such short amounts of time killed between 81 percent and 96.6 percent of the Bacillus subtilis bacteria used in the experiment.

"We did very short UV exposures, and even there we see 96 percent [of bacteria killed] over 6 hours," Schuerger told Astrobiology Magazine. "That's a very dramatic and a very positive sign that a rover wheel which sits on a platform, like MER did, has a much better chance of being sterilized prior to roll-off than a direct to ground system."

The number of survivors would likely have dropped to practically zero if the experiment had run for 7 or 12 days, Schuerger said.

By contrast, the second experiment simulated how a rover wheel in the future MSL mission would immediately come into contact with the martian surface. When the contaminated rover wheel rolled over the simulated surface, about 31.7 percent of the surface samples ended up showing bacterial growth.

But the contamination level dropped by 50 percent after 24 hours of exposure to simulated Mars conditions, such as UV radiation, low pressure, low temperature and high levels of carbon dioxide. The results pointed once again to the harshness of the martian surface environment for Earth life.

The second experiment doesn't say anything definitive about the real risk of contamination, Schuerger warned. For instance, it didn't test whether having multiple wheels rolling over the same surface area could bury microbes from the first wheel beneath the martian surface. It also didn't simulate the weight of the SUV-sized Curiosity rover that could mash even more microbes into the ground.

On the other hand, the researchers contaminated the rover wheels with perhaps 100,000 times more bacteria compared to what would realistically exist during any of the Mars rover missions. Some Mars rovers get sterilized three or four times, Schuerger said. He added that the journey through space may kill 75 percent of whatever survived after launch.

What the experiments do suggest is that just having the Curiosity rover sit still for a number of days could help kill off much of the bacteria clinging to its wheels. But the researchers still have questions to answer.

"We need to repeat these experiments with much longer time exposures to martian conditions to see if we can get to a rover wheel completely sterilized sitting on a landing pad," Schuerger explained. "We also need to see if 7 or 8 martian days would essentially get to zero amount of survivors, even if we accidentally transferred bacterial spores to the surface."

Such contamination experiments could be done more easily once humans establish a Mars colony and can work alongside their robotic rovers, Schuerger said. But for now, he will have to make do with small Mars simulation chambers on Earth.

Because of its history, 96 mile wide Gale Crater  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. Joy Crisp, MSL Deputy Project Scientist from NASA's Jet Propulsion Laboratory, explains:

"This may be one of the thickest exposed sections of layered sedimentary rocks in the solar system. 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.

"If we conclude that there is something unusual in the subsurface at a particular spot, we could suggest more analysis of the spot using the capabilities of other instruments," said this instrument's principal investigator, Igor Mitrofanov of the Space Research Institute, Russia.

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.

"Gale Crater and its mountain will tell this intriguing story," says Matthew Golombek, Mars Exploration Program Landing Site Scientist from JPL. "The layers there chronicle Mars' environmental history."

In the gentle slopes around the mountain, Curiosity will prospect for organic molecules, the chemical building blocks of life. Mars Reconnaissance Orbiter has found an intriguing signature of clay near the bottom of the mountain and sulfate minerals a little higher up. Both minerals are formed in the presence of water, which increases potential for life-friendly environments.

"All the types of aqueous minerals we've detected on Mars to date can be found in this one location," explains Golombek.

Clay settles slowly in water and forms little platelets that conform around things, hardening over time and encasing them in ''casts." Clay could seal organics off from the outside environment much like it preserved dinosaur bones on Earth.

"If organics ever existed on Mars, they could be preserved in the clay."

Even on planet Earth, teeming with life, finding billion year-old well-preserved organics is difficult. But Curiosity will find them if they're present in the samples it takes. The rover is equipped with the most advanced suite of instruments for scientific studies ever sent to the Martian surface1. When these are brought to bear on Gale crater’s mysteriously layered mountain, the odds of a discovery will be at an all-time high.

As seasoned travelers know, however, the journey is just as important as the destination. Curiosity can travel up to 150 meters per Mars day, but will stop often to gather and analyze samples.

"It could take several months to a year to reach the foot of the mountain, depending on how often the rover stops along the way," says Golombek. "There will be plenty to examine before getting to the central mound."

A high-resolution camera on the rover's mast will take pictures and movies of the scenery, taking Earthlings on an extraterrestrial sightseeing tour.

"As Curiosity climbs toward higher layers, you'll see spectacular valleys and canyons like those in the U.S. desert southwest. The walls on either side of the rover will rise over 100 feet. The sights alone will be worth the trip."

The Mars Science Laboratory mission will use 10 instruments on Curiosity to investigate whether the area selected for the mission has ever offered environmental conditions favorable for life and favorable for preserving evidence about life.

"The strength of Mars Science Laboratory is the combination of all the instruments together," Mitrofanov stressed.

The Dynamic Albedo of Neutrons instrument, or DAN, will scout for underground clues to a depth of about 20 inches (50 centimeters).

DAN will bring to the surface of Mars an enhancement of nuclear technology that has already detected Martian water from orbit. "Albedo" in the instrument's name means reflectance — in this case, how original high-energy neutrons injected into the ground bounce off atomic nuclei in the ground. Neutrons that collide with hydrogen atoms bounce off with a characteristic decrease in energy, similar to how one billiard ball slows after colliding with another. By measuring the energies of the neutrons leaking from the ground, DAN can detect the fraction that was slowed in these collisions, and therefore the amount of hydrogen.

Oil prospectors use this technology in instruments lowered down exploration holes to detect the hydrogen in petroleum. Space explorers have adapted it for missions to the moon and Mars, where most hydrogen is in water ice or in water-derived hydroxyl ions. 

Mitrofanov is the principal investigator for a Russian instrument on NASA's Mars Odyssey orbiter, the high-energy neutron detector (HEND), which measures high energy of neutrons coming from Mars. In 2002, it and companion instruments on Odyssey detected hydrogen interpreted as abundant underground water ice close to the surface at high latitudes. That discovery led to NASA's Phoenix Mars Lander going to far northern Mars in 2008 and confirming the presence of water ice.

"You can think of DAN as a reconnaissance instrument," Mitrofanov said. Just as Phoenix investigated what Odyssey detected, Curiosity can use various tools to investigate what DAN detects. The rover has a soil scoop and can also dig with its wheels. Its robotic arm can put samples into instruments inside the rover for thorough analyses of ingredients. Rock formations that Curiosity's cameras view at the surface can be traced underground with DAN, enhancing the ability of scientists to understand the geology.

The neutron detectors on Odyssey rely on galactic cosmic rays hitting Mars as a source of neutrons. DAN can work in a passive mode relying on cosmic rays, but it also has its own pulsing neutron generator for an active mode of shooting high-energy neutrons into the ground. In active mode, it is sensitive enough to detect water content as low as one-tenth of one percent in the ground beneath the rover. 

The neutron generator is mounted on Curiosity's right hip. A module with two neutron detectors is mounted on the left hip. With pulses lasting about one microsecond and repeated as frequently as 10 times per second, key measurements by the detectors are the flux rate and delay time of moderated neutrons with different energy levels returning from the ground. The generator will be able to emit a total of about 10 million pulses during the mission, with about 10 million neutrons at each pulse.

"We have a fixed number of about 10 million shots, so one major challenge is to determine our strategy for how we will use them," said Maxim Litvak, leading scientist of the DAN investigation from the Space Research Institute.

Operational planning anticipates using DAN during short pauses in drives and while the rover is parked. It will check for any changes or trends in subsurface hydrogen content, from place to place along the traverse. Because there is a low possibility for underground water ice at Curiosity's Gale crater landing site, the most likely form of hydrogen in the ground of the landing area is hydrated minerals. These are minerals with water molecules or hydroxyl ions bound into the crystalline structure of the mineral. They can tenaciously retain water from a wetter past when all free water has gone.

"We want a better understanding of where
the water has gone," said Alberto Behar, DAN investigation scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "DAN fits right into the follow-the-water strategy for studying Mars."

Mars Science Laboratory Project Scientist John Grotzinger of the California Institute of Technology in Pasadena said, "DAN will provide the ability to detect hydrated minerals or water ice in the shallow subsurface, which provides immediate clues as to how the geology of the subsurface might guide exploration of the surface.

In addition, DAN can tell us how the shallow subsurface may differ from what the rover sees at the surface. None of our other instruments have the ability to do this. DAN measurements will tell us about the habitability potential of subsurface rocks and soils — whether they contain water — and as we drive along, DAN may help us understand what kinds of rocks are under the soils we drive across."

Information from DAN will also provide a ground-truth calibration for the measurements that the gamma-ray and neutron detectors on Odyssey have made and continue to make, all around the planet, enhancing the value of that global data set.

The Daily Galaxy via nasa.gov/msl, astrobio.net and space.com

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