How can we protect Mars from Earth while searching for life?

How can we protect Mars from Earth while searching for life?
Recurring slope lineae on Mars, such as these dark streaks shown in Coprates Chasma, are possibly caused by seeping water. Credit: NASA/JPL-Caltech/Univ. of Arizona

The search for life on Mars presents us with many challenges – not the least of which is microbial contamination. How do we ensure that microbes from Earth don't hitchhike all the way to the Red Planet and spread there? When a spacecraft is on the surface of Mars, what steps are needed to protect the environment from changes that could hurt any Martian life that is there?

Finally, once we do scoop up potential microbes for analysis on Earth, how do we ensure that the Mars sample doesn't pose a risk to humans and other creatures on our planet? As biologist John Rummel recalls, the lesson of the H.G. Wells book The War of the Worlds, a fictional book about a Martian invasion, is that even microbes can be deadly.

"The important thing about is it's a two-way affair," said Rummel, who was with East Carolina University as a biologist when he led the team that published a recent study on the possibilities of the growth of Earth life on or under the surface of Mars.

"The idea is to not take microbes to places where you would have them grow and multiply on a planet, and in particular, affect the ability to find what was there before Earth contamination. We don't want to contaminate what we want to study. The other thing is, if there is any life there, it's uncertain if it would pose a danger to the Earth's biosphere if we brought a sample back robotically, or with Mars astronauts returning to Earth."

This question was considered somewhat ineffectively during the Apollo missions, Rummel pointed out, when astronauts came back to Earth and in the first few missions, were placed under quarantine for 21 days.

The crews would walk across an aircraft carrier eventually wearing nothing but masks and light jump suites, exposing the ship and its crew to potential contamination. And of course, we now know that 21 days is a short incubation period for many viruses, and for prion-spread diseases such as bovine spongiform encephalopathy (sometimes referred to as mad cow disease). The incubation time of these illnesses was not well-known at the time.

Rummel, currently a visiting scholar at McGill University, helmed a paper looking at "special regions" on Mars—locations where habitable conditions are most likely to be present—and how to protect them. Published in the journal Astrobiology in November, the paper is titled, "A New Analysis of Mars 'Special Regions': Findings of the Second MEPAG Special Regions Science Analysis Group."

Sterilization standards

A search for habitability is one of the main goals of the Curiosity rover mission, which landed on Mars in 2012. While roaming around Gale Crater, it found ample evidence of past water in the form of an ancient stream bed just months after landing. More recently, it has found that rocks on the crater floor are slanted in a way that suggests the entire area was a lakebed in the past. For how long the water persisted is one question preoccupying NASA researchers presently.

How can we protect Mars from Earth while searching for life?
The Mars Curiosity rover’s landing site restrictions included avoiding those areas with ice, in case a crash with the nuclear generator on board might melt it and created a habitable environment for hitchhiking microbes. Credit: NASA/JPL-Caltech/MSSS

Following on from Curiosity will be the Mars 2020 rover, which will again search for habitable environments, and possesses instruments that can search for organics, while caching a sample for later return to Earth. It is considered a key element in NASA's ability to stage a sample return mission from Mars in the coming decades.

There is a tension, however, in searching for habitable environments—or life—with an Earth machine while not contaminating the Martian surface. According to Rummel, Curiosity was restricted from landing in an area that could have surface or shallow subsurface ice. That's because the rover is powered by a plutonium generator, which is always hot. There was a risk that after a crash, the heat from the generator could melt the ice and provide a warm, wet pool under the surface for several months to several years, providing a potentially habitable environment for the reproduction of any earthly microbes that took a ride.

Curiosity and other modern Mars spacecraft are treated differently than the Viking landers of the 1970s, and are not fully sterilized. While the Vikings were baked for 54 hours to make them as sterile as possible, with a great deal of care and planning, this brute-force method could hurt today's sensitive electronics, and has not been required by NASA since a 1992 report of the US National Research Council suggested that Mars (not including the "Special Regions") did not require it. That is why, according to Rummel, Curiosity was sterilized to a lower standard than Viking. The standard was still enough to meet planetary protection requirements, but when it comes to Mars "special regions" the researchers didn't want to take any chances.

Temperature and water

The standards for special regions have evolved under the International Council for Science's Committee On Space Research (COSPAR), which first considered planetary protection in the early 1960s. The committee's influence is shown in the United Nations' Outer Space Treaty of 1967, which among other items says space exploration on the Moon and other "celestial bodies" must be done in a way "so as to avoid their harmful contamination."

The first successful landings on Mars took place in 1976, and the next ones happened in 1997 with NASA's Pathfinder lander mission and its Sojourner rover. With the planning of more Mars landing missions—particularly the Spirit and Opportunity rovers, which launched in 2003—the question arose about the potential for habitable regions on Mars that would be at greater risk for contamination.

COSPAR formally considered the question at a workshop held in Williamsburg, Virginia in 2002, which defined a "Special Region" as a location where Earth life could reproduce, and/or where Mars life could be found. That definition was added into COSPAR planetary protection policy the same year. In order to have a more useful definition of Special Regions, four years later the NASA Mars Exploration Planning and Analysis Group (MEPAG) made recommendations on how to define these special regions, focusing on temperature, water availability and the persistence of martian conditions over the next 100 years.

At the time, they suggested a temperature of no more than -20 degrees Celsius (-4 Fahrenheit), as there was nothing in the literature that showed microbes replicating at a temperature of -15 or lower. They could survive at lower temperatures, but not reproduce.

How can we protect Mars from Earth while searching for life?
Planetary protection for both Earth and Mars will need to be satisfied before any sample return from the Red Planet. This is an artist’s illustration of a possible concept for that mission. Credit: NASA/JPL-Caltech

"The wording of the policy was 'replicate'," Rummel said. "If you've got one unhappy little microbe on the surface on Mars hoping for a change of the weather in 100 years to replicate, you're not going to change the weather, so that's not much of a threat."

The water activity limit was defined as 0.5 on a scale between 0 (no water/no activity) and 1 (pure water/high activity). Life tends to survive in conditions ranging from thick sugar water (0.6 on the scale) to the oceans (roughly 0.95).

Mapping out the hotspots

In this latest study, the literature yielded an instance of life replicating at -18 Celsius (-0.4 Fahrenheit), which Rummel was pleased to note was within the limits of the previous study. The authors also took into account findings from the 2007 Phoenix landing mission, which examined salty soil and ice near the Martian south pole.

How can we protect Mars from Earth while searching for life?
The northern ice cap of Mars. Credit: NASA/JPL-Caltech/MSSS

"What was most interesting was that in the summer the site reached both the lower temperature limit for life and exceeded the water activity limit (through a high relative humidity), but not simultaneously," Rummel said.

One major goal was to take the findings from the literature and map out areas that are vulnerable during exploration, which would include caves and recurring slope lineae, which are locations on Mars with dark streaks where water is believed to seep through icy slopes at certain times of the year when the Sun strikes the location. Mars 2020 and similar rovers are unlikely to explore these regions, Rummel added, simply because the slope of a cave or linae would pose a risk to the rover as it may not be able to climb out again.

Rummel acknowledged there is a difficulty inherent to robotic and human explorers, who would like to get at these interesting areas but also must make sure that their efforts don't disturb any potential life that might be there. For him, to study such areas with robots, more rigorous sterilization methods are required to make sure that any contamination risk is as low as possible, so that we may keep a firewall between the planets in order to study them as they are.

Explore further

Professor helps craft marching orders for Mars rover

More information: "A New Analysis of Mars 'Special Regions': Findings of the Second MEPAG Special Regions Science Analysis Group (SR-SAG2)." Astrobiology. November 2014, 14(11): 887-968. DOI: 10.1089/ast.2014.1227
Journal information: Astrobiology


This story is republished courtesy of NASA's Astrobiology Magazine. Explore the Earth and beyond at .

Citation: How can we protect Mars from Earth while searching for life? (2015, February 3) retrieved 16 September 2019 from
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User comments

Feb 03, 2015
Mars and Earth (and every other body in our solar system) have been exchanging microbes regularly for a billion years from meteor impacts for one.... second its up to evolution to regulate and not by some not so special monkey thinking they can play god with other life forms.

Someday a microbe will come to earth (or evolve here) and wipe out mankind. We better be ready with multiple colonies off-earth and not waste time or money thinking about this kind of nonsense so we can live on to evolve further.

Feb 03, 2015
Why is it that a miscreant, feels tat WE need to "protect" whatever ? Is it an excuse to meddle in other peoples business ?

Feb 03, 2015
Thank goodness no one has any hair-brained ideas to ever send people to Mars. There would be no way that we could 'sterilize' them and their equipment (and wastes). Oh, wait; NASA is working on it. (among others) Call in the lawyers.

Feb 03, 2015
How can we protect Mars from Earth while searching for life?

We'll get nowhere acting like politically correct post modern beta males (think Obama). The Chinese, Indians and Russians are going to give this subject zero consideration, the West should afford even less.

We need to drop comets on Mars. Not worry about preserving the as good as dead Martian environment.

Feb 03, 2015
Why is it that a miscreant, feels tat WE need to "protect" whatever ?

Who else is going to do protect it?

Because: Aren't we going to feel dumb when we find out: "There was life on Mars, and it would have been great to study it - but we killed it off because we skimped on handing out hand sanitizers to NASA engineers"?

We need to drop comets on Mars.

Hello? Reality calling? What are you blathering about? (Apart from the technical infeasibility 'dropping comets' is just pointless)

Feb 03, 2015
The Mars surface is the last place to go land people. Start terraforming it by dropping our earth microbes now and start to colonize it in 10,000 years when they render it more hospitable. The cloud tops of Venus and the surface of Titan are two much better locations to land on now and to set up colonies now and well before attempting human landings on Mars.

The hell with the existing microbes or other life forms there. Humans come first when expanding into space and our survival trumps the survival of other life forms as part of life evolution

Feb 03, 2015
Dumping microbes on Mars isn't going to make it habitable.
Atmospheric density is less than 1% that of Earth. Microbes aren't going to change that. Even if you could somehow get the right composition you couldn't breathe it. it'd be like standing on a Mountain 35km high without an oxygen mask (similarly cold, too).

Speaking of composition: Mars atmosphere is mostly CO2. You need to get this to 21% oxygen, 78% Nitrogen (or some other inert filler - and where exactly is THAT going to come from?)...Also you'd need to get the CO2 level (well) below 7% or you'll just die from CO2 poisoning/suffocation.

So in the end it doesn't matter whether we dump water on Mars or try to terraform...It'll always require a full-body pressure-suit and oxygen/nitrogen tank when you go outside.

Feb 03, 2015
Ask some of the old guys from Lockheed Martin about that spot on a rock near the Viking lander. It was there when it landed and bigger the year after. L-M won't talk about it because of the "Did We contaminate Mars" argument.

Feb 03, 2015
So in the end it doesn't matter whether we dump water on Mars or try to terraform...It'll always require a full-body pressure-suit and oxygen/nitrogen tank when you go outside.

The energy required to Terraform Mars is enormous, but it is not inconceivable. The problem is it is quite honestly easier in many respects to just stay in space on Asteroids and space stations with self-sustaining biospheres.

You need to collect enormous amounts of energy from the Sun and use electric Solar sails to move matter around inside the SS. You collect Nitrogen from Titan. You get Oxygen by baking it out of the Moon Rock using Solar power.

Over multi-generational time scales you can move enormous amounts of material in that fashion.

Feb 03, 2015
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Feb 04, 2015
ALL pure DEADLY trash everywhere

Localized. Very. And it stays that way. Microbes would pose a global contamination hazard from a point source.

Feb 05, 2015
Take a look at the picture The Opportunity Rover took in 2007 0f Cape St. Vincent ,it's the only photo needed to prove the former or present existence of a humanoid presence on Mars. The highlights are a 12 meter Egyptian Style statue, a chain hoist rigging holding some material, and an excavated hole with a pile of dirt next to it, a pretty good trick for the wind. The video is titled "St Vincent 3-26-13 HD The Most Important Photo Ever Taken" on youtube WHY DOES NASA KEEP LYING TO US, THEY'RE STILL ADHERING TO THE BROOKINGS REPORT, which essentially states that all evidence of extraterrestrial contact should be kept from the public due to unfourseen effects on the the social, political and economic structures of society.

Feb 08, 2015
Has anyone ever done some sort of calculation for the maximum possible growth rate of an Earth extremophile on Mars?

It is apparently our duty to preserve life from this planet and seed it on other planets where reasonable. To this end I suggest we proceed to seeding Mars with life by any and every means available and providing means to maximize it's potential survival.

It seems to me that space programs aren't making enough discoveries lately, but this encounter with Ceres and Pluto will change that a bit. Still, we need the space program to actually be doing something constructive to continue to provide scientific and perhaps societal contributions.

Feb 10, 2015
We have been and continue to waste a lot of time and money on Mars. Mars is the last place humans should be heading for. There is noting there worth going for. It is too big to land on and take off from so any kind of base will not be possible for a thousand years.

We can land on moons and moon size objects today. We can land on an orbiting platform (floating station) with today's technology.

The two best places in our solar system to go to are:

(1) The Atmosphere of Venus with a floating space station in the habitable cloud layers where people can step out on the balcony with minimal protection. We can land and take off to a space station and then return to earth. No new tech required.

(2) The surface of Titan... we can set up a base there similar to what we have in Antarctica. We can land and take off from there like we do from the earth's moon. Plenty of fuel and water and organic molecules for making food and fuel. We don't need to take as much with us.

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