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Mars Science Laboratory

Planetary Protection

Engineers work on Opportunity (in its cruise configuration) in a cleanroom at Kennedy Space Center. A very important part of planetary protection is keeping contaminants from humans from riding aboard spacecraft. The pictured engineers are donning "bunny suits" that only allow their eyes to be exposed.

Planetary protection technologies are for cleaning and sterilizing spacecraft and handling soil, rock, and atmospheric samples. Below are examples of the way in which the Mars Science Laboratory mission benefits from past technological development and contributes new capabilities.

Inherited Technologies

In the study of whether Mars has had environments conducive to life, precautions are taken against introducing microbes from Earth. The United States is a signatory to an international treaty that stipulates that exploration must be conducted in a manner that avoids of the transportation of living organisms to celestial bodies. One reason to avoid that is simple: we wouldn't want to go to Mars and "discover" life - only to figure out later that we brought it with us! Scientists also want to study the planet and any life that might be there in its original "pristine state."

The primary strategy for preventing the transportation of Earth organisms to Mars is to be sure that the hardware intended to reach the planet is clean. The Mars Science Laboratory Rover complies with requirements to carry a total of no more than 300,000 bacterial spores on any surface from which the spores could get into the martian environment. Many of the techniques for cleaning spacecraft surfaces and then checking them for biological cleanliness have been used successfully for many years and work very well.

The cleaning techniques are effective and don't hurt the hardware. For instance, technicians assembling the spacecraft and preparing it for launch frequently clean surfaces by wiping them with an alcohol solution. The planetary protection team carefully samples the surfaces and performs microbiology tests to demonstrate that the spacecraft meets requirements for biological cleanliness.

Components tolerant of high temperature, such as the parachute and thermal blanketing, are heated to 110 degrees Celsius (230 Fahrenheit) or hotter to eradicate any microbes. The core box of the rover, containing the main computer and other key electronics, is sealed and vented through high-efficiency filters to keep any microbes inside. Some smaller electronics compartments are also be isolated in this manner.

Another type of precaution is to be sure that other hardware doesn't go to Mars accidentally. When the Atlas launch vehicle's third stage separated from the spacecraft, the two objects were traveling on nearly identical trajectories. To prevent the possibility of the third stage hitting Mars, that shared course was deliberately set so that the spacecraft made a final trajectory correction maneuver about 10 days after separation, allowing the spacecraft to arrive at Mars while the third stage missed the planet completely.

New Capabilities:

While the methods for cleaning and testing for biological cleanliness are well understood, some things about Mars Science Laboratory posed extra challenges for planetary protection and some new techniques were used.

The primary challenge posed by Mars Science Laboratory in the area of planetary protection is that it is so much bigger than earlier Mars landers. Because it is bigger, there was more surface area to clean and test. That resulted in more time and effort. Also, because the planetary protection cleanliness requirement is a per-spacecraft requirement, it is harder to meet the requirement the larger the spacecraft gets!

Mars Science Laboratory used two new technologies to streamline the assessment of whether the spacecraft was biologically clean enough to meet its planetary protection goals. These are newer and faster ways to measure whether the surfaces are clean enough for engineers to proceed to the next level of assembly. One is called the Limulus Amebocyte Lysate (LAL) Assay and the other is the Adenosine Triphosphate (ATP) Assay. Each detects the presence of molecules that are typically associated with microbes that might still be on the hardware and takes less than an hour. If results from the LAL and ATP Assays are low (good) enough, then assembly may continue. To meet the formal planetary protection cleanliness requirement, Mars Science Laboratory also used the traditional 3-day biological assay that checks for bacterial growth in cultivation dishes.