APOD: Juno Rockets Toward Jupiter (2011 Aug 09)

[Chris Peterson]

I'm still not clear on the need to avoid contamination of Europa. We have sent many probes to other bodies, including Mars, Venus and Titan. Perhaps those probes went through a complete serilization process? I find it hard to believe that we could guarantee that there were absolutely no bacteria, viruses or other critters on a probe as it leaves our atmosphere. Also wouldn't Jupiter's radiation kill off anylife after a year in orbit?

Many probes undergo some degree of sterilization. Venus and Titan are presumably sufficiently hostile to any sort of microscopic Earth life that there is little risk of contamination. Not so Mars or Europa. That we may have contaminated Mars despite our best efforts is a real concern; avoiding any contamination of Europa is considered important.

[neufer]

No bugs please, this is a clean planet!
30 July 2002

<<When packing for a trip towards another planet, there are some things, such as microorganisms, that you do not want to include in your 'luggage'. For example, what if extraterrestial life is finally detected on Mars, and scientists realise afterwards that such life is actually terrestrial?

Fortunately, there are strict international rules to avoid the contamination of Solar System bodies with biological material from Earth. Landers, for example, may present a special danger to the objects they set down on. The European Space Agency (ESA) is well aware of this. ESA's missions, such as Mars Express, with its lander Beagle 2, Rosetta, which will land on a comet, and Cassini-Huygens, headed towards Saturn and its moon Titan, will be 'clean' and responsible visitors. The strictest of procedures will ensure that they carry only highly sterilised landers.

Cassini (with Huygens on-board) left Earth in 1997 and is travelling towards the planet Saturn. In 2004, Huygens will separate from the spacecraft and land on its own on Saturn's largest moon, Titan. Titan is a highly promising site for the scientists because its atmosphere very much resembles that of primitive Earth. It is a very cold place, with temperatures down to -180ºC. Many scientists think such freezing temperatures are precisely the reason why life never arose on Titan. However, Huygens may well give them reasons to reconsider.

Rosetta and Mars Express will be launched in 2003. Rosetta is ESA's comet-chaser. It will spend 8 years travelling through the Solar System and in 2011 it will land on Comet 46 P/Wirtanen, making Rosetta the first spacecraft ever to land on a comet. Mars Express is the next mission to Mars and the first European one. It will arrive on the Red Planet in December 2003 and release its lander Beagle 2, whose task, among others, is to search for evidences of Martian life.

These diverse projects all have something in common. They have all had to take into account the 'planetary protection' requirements set by the international scientific organisation, Committee on Space Research (COSPAR).

"We don't want to contaminate the planets we go to," says John Bennett, of ESA's Mars Express team and one of the scientists responsible for 'protecting' the Red Planet from an undesired terrestrial invasion. "We don't want future missions to detect contamination, instead of life."

COSPAR rules determine a spacecraft's degree of cleanliness. Standards vary depending on both the type of mission and its 'destiny'. For example, from a contamination point of view, landers are obviously more 'dangerous' than orbiters. Moreover, the more likely a planet is considered to bear life, the stricter the requirements are.

For these reasons, rules are especially tough for Mars Express's lander, Beagle 2. Scientists set sterilisation criteria of 300 microorganisms per square metre for missions to Mars in the past. At this level, no life was detected and they concluded that this sterilisation level would not compromise or affect biological measurements. Beagle 2 will have to be sterilised to contain less than 300 microorganisms per square metre at launch, and no more than 300 000 inside the whole launcher. By comparison, the floor of even the cleanest kitchen inside a house on Earth has several thousands of millions of microorganisms present.The sterilisation process is quite complicated. Many of the instruments' components are very delicate and would not withstand very high temperatures, so scientists use different techniques.

They will heat most of the components of Beagle 2 to 120ºC and clean other components chemically. For the solar panels, for example, an alcohol will be used. The microelectronics components will be placed in a vacuum chamber with a special gas, hydrogen peroxide plasma, that oxidises biological material, making it harmless. Scientists will also use another sterilising technique, irradiation with ultraviolet light and other kinds of radiation. Sterilisation will affect all parts of the lander, even the airbags and the parachute system the lander uses to reach the ground safely. For Beagle, the process will take place in several facilities in the United Kingdom. Special transportation systems will take each component to a specially built clean room where they will be assembled on location at the Open University site in the United Kingdom. Assembly will begin this summer. Once finished, the ultraclean Beagle 2 will be 'sealed' within its own front-shield and back-cover, and made ready to be mounted on Mars Express.

Requirements for Rosetta and Huygens are less strict. When Cassini-Huygens was launched in 1997, scientists thought that life was simply too unlikely to exist on the cold Titan. They therefore labelled the project low risk, with no sterilisation procedures considered necessary. However, according to COSPAR rules, the spacecraft was assembled in a clean room, that is, with less than 100 000 particles per unit of volume.

Rosetta is a similar case. "Sterilisation is generally not crucial since comets are usually regarded as objects where you can find prebiotic molecules, that is, molecules that are precursors of life, but not living microorganisms," explains Gerhard Schwehm, Rosetta's Project Scientist. On the other hand, Rosetta has to perform delicate experiments on the comet and scientists do not want the results to be spoiled, so cleanliness is required.>>

[NoelC]

Meh, the likelihood of a probe crashing into Europa and infecting it seems awfully small compared to sending one there on purpose to land...

Actually, from a "propagation of life as we know it" perspective, why wouldn't we want to send flora and fauna to all the rest of the bodies in the Solar System? It might actually be comforting to think that something we deposited might survive on Mars or Europa after we have a sterilizing asteroid impact here (or, more likely, unleash enough radiation ourselves to kill everything including cockroaches).

I suppose there's some scientific justification for wanting to try to find out definitively if there already was a form of life on Mars or Europa or wherever, but after that... ??? Start the terraforming!

Sending microbes to Mars may sound like a Bad Thing to strive against, yet (eventually) sending humans there is actively being considered. I'm sure people are dreaming of walking on (or swimming under the surface of) Europa one day as well. Is someone being a bit penny wise and pound foolish here?

Seems like the brilliant minds don't have all the policies completely worked out.

Neufer, please feel free to free associate with War of the Worlds now.

-Noel

[Chris Peterson]

Meh, the likelihood of a probe crashing into Europa and infecting it seems awfully small compared to sending one there on purpose to land...

Actually, the probability is quite high. A probe in orbit around Jupiter inside the orbit of the Galilean moons will almost inevitably end up hitting one of them. It has to do with the instability their gravitational perturbations introduce.

I suppose there's some scientific justification for wanting to try to find out definitively if there already was a form of life on Mars or Europa or wherever...

You think?! <g>

[neufer]

Sending microbes to Mars may sound like a Bad Thing to strive against, yet (eventually) sending humans there is actively being considered. I'm sure people are dreaming of walking on (or swimming under the surface of) Europa one day as well.

Neufer, please feel free to free associate with War of the Worlds now.

I don't know about the Martians but I see little chance of us ever getting involved in a European War...they are simply too far away.

[Beyond]

I don't know about the Martians but I see little chance of us ever getting involved in a European War...they are simply too far away.

Can you spell WW1, WW2 and intercontinental ballistic missile

[NoelC]

Meh, the likelihood of a probe crashing into Europa and infecting it seems awfully small compared to sending one there on purpose to land...

Actually, the probability is quite high.

But what's the probability it would burn up or crash violently? Or is it also likely it would glide right through the (very thin oxygen) atmosphere and land in such a way that microbes could survive?

-Noel

[Chris Peterson]

But what's the likelihood it would burn up? Or is it also likely it would glide right through the (very thin oxygen) atmosphere and land in such a way that microbes could survive?

It would not burn up. Europa's atmosphere would be called a hard vacuum in a lab. The spacecraft wouldn't even get warm. How much energy actually got released in the impact would depend on the velocity, which could cover a wide range. But people have looked at the dynamics of both meteorite entries and reentering space junk on Earth, and found that microbes can survive both. With no effective atmosphere and a much lower gravitational field, it is certain that microbes on a spacecraft could survive a collision with Europa.

Again, as what is arguably the most likely body in the Solar System to harbor extraterrestrial life, it is reasonable for researchers to be cautious, which is why there is an agreement to design Jupiter missions in a way that attempts to avoid leaving any uncontrolled things in orbit.

[NoelC]

Fair enough. It's good that scientists are being respectful of possible extraterrestrial life, though it's really quite hard to imagine that will continue if mankind goes into space in a big way.

-Noel

[Sam]

Consider also the mayhem and speculation that would ensue if we were to find, on another world, life so closely related to our own.

The cases for the two opposing hypotheses,
- "Life originated on Mars and came to Earth!"
vs.
- "Life originated on Earth and went to Mars!"
would become a bit more confused.

[neufer]

Sending microbes to Mars may sound like a Bad Thing to strive against, yet (eventually) sending humans there is actively being considered. I'm sure people are dreaming of walking on (or swimming under the surface of) Europa one day as well.

Neufer, please feel free to free associate with War of the Worlds now.

http://www.imdb.com/video/hulu/vi3385000729/

[NoelC]

Consider also the mayhem and speculation that would ensue...

Yet, beyond fueling man's insatiable appetite for debate (which is far easier to partake in than doing real work), it would mean absolutely nothing. Life would go on.

Don't I recall that some meteorites have been found that have been speculated to be pieces of Mars? There may have been some "life swapping" already.

-Noel

[NoelC]

http://www.imdb.com/video/hulu/vi3385000729/

Sorry, I couldn't get past the ad fest. I'm sure it was an interesting episode.

-Noel

[Chris Peterson]

Fair enough. It's good that scientists are being respectful of possible extraterrestrial life, though it's really quite hard to imagine that will continue if mankind goes into space in a big way.

I think it's less about respect and more about wanting to avoid ruining some really good science opportunities.

It remains to be seen if man will go into space in "a big way", but if that ever happens, the ethical, practical, and scientific implications of our contaminating or being contaminated will have to be addressed then. For now, Mars are Europa are probably the only bodies where caution is really warranted.

[Chris Peterson]

Don't I recall that some meteorites have been found that have been speculated to be pieces of Mars? There may have been some "life swapping" already.

Yes, there are Martian meteorites, and some researchers do take seriously the possibility that organic molecules, if not life itself, might have been transferred to Earth by that route. Getting Earth material to Mars is a lot more difficult, and therefore less likely.

If life is found on Mars which uses the same cellular chemistry as life on Earth, people will have to look very closely at the issue of possible contamination from our exploration.