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Curiosity Rover May Have Brought Dozens of Microbes To Mars
bmahersciwriter (2955569) writes "Despite rigorous pre-flight cleaning, swabbing of the Curiosity Rover just prior to liftoff revealed some 377 strains of bacteria. 'In the lab, scientists exposed the microbes to desiccation, UV exposure, cold and pH extremes. Nearly 11% of the 377 strains survived more than one of these severe conditions. Thirty-one per cent of the resistant bacteria did not form tough, protective spore coats; the researchers suspect that they used other biochemical means of protection, such as metabolic changes.' While the risk of contaminating the red planet are unknown, knowing the types of strains that may have survived pre-flight cleaning may help rule out biological 'discoveries' if and when NASA carries out its plans to return a soil sample from Mars."
It has been speculated that life here on Earth came from space. And there has been speculation that this life may have come from Mars thanks to asteroid impacts ejecting material with enough energy to reach escape velocity, some of this material reaching the Earth in its early primordial history. Well, if this is the case, we're returning the favor.
It's really quite a simple choice: Life, Death, or Los Angeles.
JPL actually has a highly detailed document on "Policy for Planetary Protection" that details the standards to which a probe must be sanitized to before being sent on its mission. The level of cleanliness depends on the intended mission and target; orbiters have a lesser standard than landers, for example. The policy also takes into account different parts of the spacecraft; the inside of the box containing the CPU and so forth isn't cleaned to as high of a standard as the wheels, experiments and so forth that are directly exposed to the environment. In the case of the Galileo probe, it was deliberately crashed into Jupiter at the end of mission in order to ensure it would never impact Europa, as it had not been cleaned to that high of a standard. Cassini will face a parallel fate, of crashing into Saturn to prevent a collision with Enceladus and/or Titan.
The key part here is that when you are looking for life (or might be looking for life in the near future) you don't want to discover that the life is found is something that you brought from earth yourself, or was brought by another space probe.
...si hoc legere nimium eruditionis habes...
First properly documented interplanetary flight sent by us, with biological specimens on board ! Pity we didnt measure the effect of zero-g or deep space radiation on these.
It's actually assumed that every probe that is sent will have some form of bacteria and so forth on it; life is just so pervasive on this planet that it's impossible to perfectly sterilize everything. Instead, the goal is to strongly sterilize what's critical and exposed to the environment, and reduce the probability of accidental contamination to an acceptable level (currently defined to be in the neighbourhood of 1 in 10,000 chance).
...si hoc legere nimium eruditionis habes...
It's easy enough to simulate martian conditions here on earth, which is a more controlled and far cheaper means of experiment. It was found that certain lichen can do quite well, although note that this was on the assumption that water would be available.
It would probably be best not to introduce earth microbes before a full terraforming plan is developed. The population might explode, consume all the available micronutrients, and then die off. Or it might become a pest, inhibiting the release of other, more useful microorganisms later on. And it might obscure any extant martian microorganisms or micoorganism fossils when those could provide a far better template than earth-based extremophiles. We'll want something robust and sustainable, a planned ecosystem genetically engineered to produce all the right byproducts and which changes in concert with the alterations to atmosphere, global temperature, and soil composition without any unintended extinction events.
When things get complex, multiply by the complex conjugate.
To add to this, also sterilize it to practical limits given danger to the flight hardware. Many of the early Ranger lunar-impact missions had hardware failures on the way, eventually strongly suspected to have been caused by damage due to heat-sterilization:
http://ntrs.nasa.gov/archive/n...
Once they backed off on the degree of sterilization, the rate of random failures dropped dramatically.