[meteorite-list] Life's Rocky Road Between Worlds

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:12 2004
Message-ID: <200106121942.MAA14478_at_zagami.jpl.nasa.gov>

You bring up some good points.

> "The long term average transfer rate of 150kg of hospitable rocks per
> year,
> with 7% of resident microbes surviving (if any were present in the rocks
> at
> the time of launch), is equivalent to a series of space missions that
> return samples of about 10 kg of Martian rocks each year under protected
> conditions that are favourable to the survival of any life within the
> rocks."

To date, we haven't found any surviving microprobes in any of the Mars meteorites.
ALH84001 only involved potential microfossils.
 
> So what makes the small samples returned to Earth by our spacecrafts so
> threatening?

The main difference is the amount of time the samples spend in space enroute
to Earth. For the typical Mars meteorite, it would have been in space for 15
to 30 millions years before it landed on Earth. For a sample returned by
spacecraft, the sample would only spend a few months in space enclosed in a
container. Any Mars organisms, if present, would have a much higher likelihood
of surviving the trip from Mars to Earth in a spacecraft than in a Mars meteorite.

Ron Baalke
Received on Tue 12 Jun 2001 03:42:43 PM PDT