The search for life

Ken Tapping, July 31, 2013

In the sky this week…

  • Venus lies low in the west after sunset. Saturn lies in the Southwest overnight.
  • Mars and Jupiter lie close together in the dawn twilight, with Mercury lower down. Look for Mercury low in the dawn sky.
  • The Moon will be New on 6th August.

In one of the science fiction stories I read a long time ago, our first explorers on Mars were surprised by an alien being who came out of the Martian desert and announced its life processes were based on the element silicon. That struck me as an extremely unlikely introduction, which was of course in English. When we do first find life on other worlds, it is more likely to be bacteria or simple plants and animals. Even on Earth today they are the most common forms of life. It is very likely that they will not come forth and announce themselves; we will have to search for them.

Here on Earth it is hard to find places where there are no living things. They have even colonized environments that are hostile to us, such as near-boiling, mineral-laden water, and rock cavities kilometres underground. In the 1960’s, one of the Lunar Surveyor spacecraft took bacterial stowaways along with it. They were still living on the Moon years later, when Apollo astronauts visited its landing site. They had survived years in a vacuum, with large temperature variations and high levels of radiation. The rule seems to be that if living creatures can get somewhere, they will make a serious attempt to colonize that place.

This leads to some interesting points when we go looking for life on other worlds. It could be that if conditions are remotely suitable, life will make a serious attempt to get going there. However, it also means that we should try not to take unintended colonists along with us. Our ambassadors to other worlds have to be as sterile as we can make them.

The Apollo astronauts landed on the Moon in what was essentially a one-room spacecraft. To get to the lunar surface they had to put on space suits and then vent the air from the spacecraft, open the door and crawl out.

Human beings, along with all our cousins in the animal kingdom are not very clean. We carry along more than half our weight in bacteria. Our skins are covered with them. As we move around, we shed bacteria, dead skin, hairs and perspiration. That does not include whatever we breathe out. The air in the Apollo lander was loaded with that stuff; it was vented out onto the Moon. The space suits would have been covered with our debris too. We don’t know how high the contamination risk is for the Moon; although we know there is one. However, for Mars and other worlds with atmospheres the issue could be a lot more serious. This subject is getting a lot of discussion around the science community at the moment.

Unless we use spacecraft that are large enough to carry along effective sterilization systems for cleaning unwanted passengers from equipment and the exteriors of space suits, it might not be practical for the initial life search missions to involve astronauts at all. Maybe it would be better to continue to send robots until we know that sending people won’t cause unwanted environmental contamination. It is possible to render instrumentation and robots highly sterile, using processes that would kill a human being.

Years ago, science fiction writer Arthur C. Clark wrote a short story about the first manned expedition to Venus. The intrepid explorers did their thing, dumped their garbage and left. Rudimentary Venusian life forms found the garbage and the terrestrial bacteria in it, and the resulting pandemic wiped out life on that planet before we even knew life was there. This does not mean that there should be no manned exploration of the universe. We need to do that. It just means we need to do it carefully, with proper preparation.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory, Penticton, BC, V2A 6J9.

Telephone: 250-497-2300
Fax: 250-497-2355
E-mailken.tapping@nrc-cnrc.gc.ca

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