[meteorite-list] Microbes From Edge Of Space Revived

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:53:35 2004
Message-ID: <200212171723.JAA11413_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/news/news.jsp?id=ns99993186

Microbes from edge of space revived
Jenny Hogan
New Scientist
December 17, 2002

Microbes collected from the edge of space have been brought back to life in
the lab.

This enabled the high-flying organisms to be identified, almost two years
after they were found in air samples collected by a weather balloon cruising
at 41,000 metres (135,000 feet) over southern India.

The two species of bacteria (B. simplex, S. pasteuri) and one fungus (E.
albus) are similar to common ground-dwelling microbes which lurk in soil and
vegetation, says Milton Wainwright of the University of Sheffield, UK, who
worked out how to culture the cells.

How the bugs got there is not known, but there are three possibilities: they
were carried up on winds, they sneaked into the samples on Earth or they
have flown through space and are aliens making their way down to our planet.

The latter possibility fits with a theory developed by Chandra
Wickramasinghe and the late Fred Hoyle in the 1970s, which proposes that
life originated elsewhere in the Universe and hitched a lift to Earth on a
passing comet.

Wickramasinghe, at the Cardiff University Centre for Astrobiology in Wales,
is Wainwright's co-author on the new paper, along with the Indian scientists
that sent up the balloon. If the microbes were indeed drifting in from
space, Wickramasinghe calculates that up to a tonne could be landing each
year, based on the density of microbes found in the air samples.

Up draught

Wainwright admits that the simplest explanation is that the organisms, found
above 99 per cent of the Earth's atmosphere, have terrestrial origins. But,
he asks, how did they get up there?

Turbulent winds at ground level are certainly capable of sweeping particles
up into the atmosphere. But this kind of weather is confined beneath the
tropopause, which acts like a lid at about 17,000 metres.

Volcanic eruptions can push matter through the tropopause. But there were no
such events in the months before the samples were taken, and gravity would
be expected to drag any microbes back down in a few days.

However, the man-made greenhouse gases called CFCs have been found at
similar altitudes, showing that global air currents can pierce the
tropopause. Martin Juckes, an atmospheric scientist at the Rutherford
Appleton Laboratory, UK, says that air flows upwards at the tropics at about
one metre per hour, and may carry material with it. But whether particles as
large as microbes could be carried to such heights is not known.

Freeze-dried

The third possibility, that the microbes represent experimental
contamination, is dismissed by Wainwright. The experimental protocol was
carefully designed to exclude contamination before the samples were
collected during the balloon flight (New Scientist print edition, 4 August
2001).

And contamination after the samples had been returned to Earth is unlikely,
he argues, because the microbes were freeze-dried. This was due to the cold,
dry conditions at 41,000 metres, he says.

To coax them into growing, Wainwright had to soak them in a nutrient
solution. They refused to multiply when spread on the jellies usually used
to culture samples - but any contaminant cells would have shown up at this
stage, he says.

Journal Reference: FEMS Microbiology Letters) (Article 10778)
Received on Tue 17 Dec 2002 12:23:57 PM PST