Biological debris on Mars

If at some future time evidence of biological presence on Mars is ever
discovered (e.g. bacteria), how will scientists be sure it's not just
contamination from previous Earthcraft that landed there?

Surely NASA doesn't claim that it's probes etc are guaranteed sterile when
they land... or do they?

Orilly


(Named after the time I get up)

Orilly wrote:
If at some future time evidence of biological presence on Mars is
ever
discovered (e.g. bacteria), how will scientists be sure it's not just

contamination from previous Earthcraft that landed there?

DNA testing. Earth bacteria aren't likely to be mistaken for martian
bacteria.

Surely NASA doesn't claim that it's probes etc are guaranteed sterile
when
they land... or do they?

No guarantees are made, but NASA has been trying.

Mike Miller

Actually, NASA tried with Viking landers and there was an attempt by
treaty at a no-contact with Mars for 50 years (expires in 2019),
meaning that even unsterilized orbiters had to be in orbits that will
not impact the planet for that long. (The reasoning at the time
apparently was that by then, manned landings would have determined the
question.)

It's not NASA that you should worry about having contaminated Mars; the
Soviets were a lot more lax in sterilization than they probably should
have been. Their technique for navigation was basically put the probe
on an impact trajectory, then move to flyby or orbit in the last
several days before encounter. At least one unsterilized probe meant
for a flyby failed while still on the impact trajectory (Zond 2), and
is thought by some to have crashed on the planet in 1965. And of course
there were Mars Observer (1992) and Climate Observer (1999), both of
which were unsterilized orbiters which may have hit the planet.

In article ws.net,
Orilly wrote:
If at some future time evidence of biological presence on Mars is ever
discovered (e.g. bacteria), how will scientists be sure it's not just
contamination from previous Earthcraft that landed there?

Given the harshness of the Martian surface environment, it's grossly
unlikely that any bacterial hitchhikers on past spacecraft have grown and
spread. Any contamination will almost certainly be in the immediate
vicinity of recognizable debris.

Martian life, if there is any, is far more likely to be found underground,
in places like hydrothermal vents. No spacecraft have been there.

Surely NASA doesn't claim that it's probes etc are guaranteed sterile when
they land... or do they?

The Viking landers were indeed sterilized -- necessarily, since they were
carrying life-detection instruments. More recent landers are not, but
efforts are made to reduce the level of bacterial contamination, precisely
to minimize the chances of confusing later life-detection efforts.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

"Orilly" wrote in message
eenews.net...
If at some future time evidence of biological presence on Mars is ever
discovered (e.g. bacteria), how will scientists be sure it's not just
contamination from previous Earthcraft that landed there?


DNA testing would be a good place to start.

wrote:

DNA testing. Earth bacteria aren't likely to be mistaken for martian
bacteria.

Why do you say that? 99% of the bacteria in any terrestrial soil sample
are from species that have not yet been identified, and there's a good
chance that, if Mars life exists, it shares a common origin with terrestrial
life.

Paul

Paul F. Dietz wrote:
Why do you say that?

Because, despite any similar origins, there's probably going to be some
obvious genetic differences. Those bacteria in terrestrial soil do not
have genes so strikingly different from identified terrestrial bacteria
that scientists might suspect they're alien, like some do with the odd
Archae microbes.

Mike Miller