Aug. 6: Aerospace and materials engineers had given the Curiosity spacecraft and rover alcohol sponge baths and oven roasted their components before their launch last year to minimise the risk of microbes from Earth riding piggyback to Mars.
The US National Aeronautics and Space Administration says the decontamination procedure is a routine step to avoid the introduction of microbes from Earth on Mars through robotic spacecraft. The decontamination is required under an international outer space treaty that stipulates that space exploration must be conducted in a manner that avoids harmful contamination of celestial bodies.
Nasa's Mars Science Laboratory spacecraft safely deposited the robotic rover today on the surface of Mars where it is expected to spend two years looking for chemical signatures of microbial life, if any, in the planet's soil and rocks.
"The treaty specifies the cleanliness of the spacecraft ' especially those going to look for organic compounds on Mars," said Scott Hubbard, an astronomer at Stanford University who is among the founders of the multidisciplinary science of astrobiology.
The mission is allowed to carry up to 500,000 bacterial spores ' about one-tenth the bacterial load in a teaspoon of seawater ' on the entire flight system, Nasa said in a backgrounder document on the mission.
Some spacecraft parts such as the heat shield and the descent stage have hit the ground so hard that they are likely to have shattered. Nasa said decontamination is achieved through two common processes -- alcohol wipe-cleaning and dry heat.
Some spacecraft and rover surfaces are cleaned by wiping them with alcohol and other solvents while other components that can tolerate heat are subject to 110 degrees C to 146 degrees C for up to 144 hours to reduce the load of spores.
Hubbard said during routine operations of the rover, several "organic check samples" will be run through the system periodically to be certain that the major instruments are free of contamination.
"Any bacteria from Earth carried to Mars will most likely perish in the harsh Martian environment," said Milind Watve, a senior microbiologist at the Indian Institute of Science Engineering and Research, Pune, who has no connection with the Curiosity mission.
"However, if some microbes do survive, we cannot predict how they'll grow or how they'll evolve in the new environment," Watve told The Telegraph.
Nasa said studies were conducted on various materials, including paint, rocket propellants, and adhesives to determine the number of spores they could carry during the mission. Such materials were exposed to dry-heat decontamination.
"But no sterilisation or decontamination process can be said to be 100 per cent successful -- the microbial population in a decontamination procedure follows a negative exponential curve, the population never goes to zero," Watve said.