Technicians and engineers test the robotic arm on NASA's Mars rover Curiosity on Sept. 3, 2010 inside the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Photo by NASA.
Imagine this crazy scenario: A space vehicle we've sent to a distant planet to search for life touches down in an icy area. The heat from the spacecraft's internal power system warms the ice, and water forms below the landing gear of the craft. And on the landing gear is something found on every surface on planet Earth... bacteria. Lots of them. Specifically spore-forming bacteria which can survive extremely harsh conditions, for years. If those spore-forming bacteria found themselves in a moist environment with a temperature range they could tolerate, they might just make themselves at home and thrive and then, well... the extraterrestrial life that we'd been searching for might just turn out to be Earth life we introduced.
This scenario is actually something NASA takes seriously. VERY seriously. During a recent trip to NASA's Jet Propulsion Laboratory in Pasadena, Calif., for a story NewsHour correspondent Spencer Michels and I were shooting on the Mars Curiosity Mission, I overheard a scientist talking about the Planetary Protection program for Mars. Huh? It had never occurred to me that the celestial bodies in our solar system might need protecting from an earthly invasion. Isn't it supposed to be the other way around?
Watch VideoNewsHour's Spencer Michels reported last month on the latest from NASA's Curiosity rover and its mission to Mars.
It turns out that the scientific community has been worried about "contaminating" solar system bodies -- planets, moons, comets, and asteroids -- with Earth life for a long time. In 1967, the U.S. signed the United Nations "Outer Space Treaty" which stated that all countries party to the treaty, "shall pursue studies of outer space, including the moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination."
Today NASA has an Office of Planetary Protection, and with each new space mission, hundreds of scientists and engineers are responsible for ensuring the spacecraft we're sending into outer space are biologically "clean." One of the key scientists making sure we don't spread Earth life to Mars is Dr. Karen Buxbaum, a planetary protection officer for JPL's Mars Program.
"We have to make sure with each successive mission we send to learn more, we don't inadvertently contaminate the place with Earth life, which would confuse our experiments," said Buxbaum.
She explained the painstaking procedures that NASA implemented to ensure the Mars Science Laboratory -- aka Curiosity -- wasn't carrying an unacceptable amount of spore-forming bacteria when it lifted off on November 26, 2011.
"When we land any spacecraft on Mars, we have certain cleanliness standards that are well-defined and methods for achieving those standards," Buxbaum said.
In the case of Curiosity, it was determined that the entire flight system could launch with no more than 500,000 bacterial spores on board. That may seem like a lot, but NASA says that's about one-tenth the number of spores found in a teaspoon of seawater.
How do you clean one of the most scientifically advanced pieces of research equipment ever sent into space? Very carefully. The process begins in the Spacecraft Assembly Facility at JPL which is a giant "clean room" where Curiosity and other rovers have been built by NASA engineers and technicians. The facility has a sophisticated airflow system which keeps particles in the air very low, and the tools and large equipment in the room are kept sterile.
"All the people who go into the room wear bunny suits," Buxbaum said. "Their boots are taped, they have masks over their faces, and they wear eye glasses." There's even a special type of paper used in the room that doesn't shed lint.
Much of the hardware used for Curiosity was built in other facilities around the country, and Buxbaum said that stringent cleaning protocols were in place at those locations as well. When shipments of equipment arrived at JPL, they were tested for live microorganisms and then wiped down before entering the clean room.
Throughout the assembly process, NASA technicians used both heat and alcohol to keep Curiosity's hardware as spore-free as possible. Pieces of equipment that could tolerate high heat were subjected to temperatures of 230 to 295 degrees Fahrenheit for up to 144 hours. And surfaces were wiped down with alcohol and tested regularly.
Special care was given to surfaces that would come in contact with the Martian surface, and possibly break apart on impact, Buxbaum said. For example, the internal surfaces of the sky crane, which lowered the rover to the surface of Mars, and the heat shield had to be cleaned.
"The parachute was huge," Buxbaum said. "The entire parachute was subjected to the standard heat protocol. It would have had a lot of microbes on it."
All of the hard work apparently paid off. According to NASA's website: "The team found Mars Science Laboratory to be extremely clean: the final bioassays found a total of 278,000 spores on the entire flight system, with 56,400 on the surface of rover hardware."
Even with all the precautions taken, if evidence of life did emerge on Mars, scientists would want to do rigorous testing to ensure it wasn't a "false positive" discovery. According to Buxbaum, "It could be very difficult to distinguish between Earth life and Mars life, depending on how the observations were made. Biomolecules, such as the DNA that exists in Earth life, have very distinctive characteristics, or 'fingerprints.' If DNA were detected in Mars samples and the DNA were found to have identical sequences to Earth organisms, microbiologists would most likely conclude that the DNA was from our spacecraft. However, if DNA or something like it were detected and found to be very different from that of known Earth organisms, then things would get pretty exciting indeed."
The concept of planetary protection isn't just something NASA is concerned about for Mars and other planets we may visit in the future. It's also something the agency is increasingly focused on as it starts to make plans to bring samples from those places back to Earth.
"We have to be humble about the kinds of things that could happen, but draw from our experiences with ecosystems and biology on Earth," Buxbaum said. "We've learned the kinds of things that can have unintended consequences in biological systems. You don't want something to come back that could infect human beings. We don't want the unintended consequence of bringing back an invasive life form that finds a habitat on earth that is conducive to its life. Even though it is unlikely, we need to look at samples before we bring them back."
Whether life does, or did exist on Mars is the subject of much speculation these days as Curiosity explores, drills, and analyzes Martian rocks. And NASA recently announced it will be sending another rover to Mars in 2020. Whether that mission will have the capabilities to bring samples back to Earth is not yet known, but rest assured, Dr. Buxbaum and her colleagues at NASA are already thinking about planetary protection procedures for us.
Photo credit: In a clean room at NASA's Kennedy Space Center, Mars Science Laboratory personnel sample the inboard side of the spacecraft's heat shield to confirm its cleanliness before final assembly for launch. Photo by NASA.