[meteorite-list] The Meteoric Rise of Life?

[Ron Baalke]

http://www.space.com/24182-meteorite-life-origins.html

The Meteoric Rise of Life?
Robin Wylie
University College London   
January 06, 2014

The silent missiles that flit between the planets have been blamed for 
some of the largest exterminations that life on Earth has had to endure: 
However you like your mass extinctions, high on the list of potential 
triggers is usually a close encounter with a meteorite.

Recently, however, a remarkable discovery has cast these aerial assaults 
into a surprising new light - because, as well as destroying life, it 
now seems that ancient collisions might also have helped create it.

In September 2013, a study appeared in the journal Nature Geoscience that 
set out to test an extraordinary theory regarding life's deep roots. Researchers 
had previously hypothesized that, through a process known as shock synthesis, 
the extreme conditions generated by meteorite impacts - specifically ones 
involving comets - might be able to forge the fundamental chemicals of 
biology. With the shock as a catalyst, the theory went, the organic 
(carbon-bearing) molecules present in the ice of comets - such as ammonia 
and methanol, a simple alcohol - could be transformed into amino acids, the 
crucial components of proteins, and therefore of life. 

It was a powerful idea, but with a complete lack of experimental evidence, 
an idea was all it was. To remedy the situation, a team of planetary scientists 
- led by Zita Martins of Imperial College London - set about re-creating 
an apocalypse in their lab. By preparing mixtures of ice and organic molecules 
that mimicked the composition of a comet, and shooting each of them with 
a high-velocity steel pellet, they managed to replicate in miniature the 
conditions created when one of those colossal bodies collides with a planet. 
The researchers then passed the shattered residue from the pellet shots 
through a mass spectrometer, to measure what new molecules, if any, had 
been produced by the shock. Amazingly, the paper reports that the impacts 
generated not just one amino acid, but eight of them.

This experiment, though a simple one on the surface, has returned a result 
with the potential to radically change our perception of how life might 
first have arisen. "We have showed experimentally for the first time that 
amino acids can be produced when a comet impacts a planetary surface," 
Martins said in a statement. At once destructive and creative, the scaled-down 
impacts have revealed that the bombardment of the young Earth - already 
thought to have given us our moon - might also have left behind some of 
the essential ingredients of life.

But thrillingly, aside from this already ground-breaking insight, another 
possibility has been raised: the implications of these findings might 
not be confined to the Earth. Practically every extraterrestrial surface 
scientists have imaged is covered with the scars of ancient meteor collisions; 
and if a comet strike could create amino acids on our planet, it could 
potentially do the same on others. According to Martins and her colleagues, 
their discoveryalso "increases the chances of life originating and being 
widespread throughout the solar system."

It's a tantalizing prospect. So tantalizing, in fact, that it has inspired 
a new voyage to a gas giant. Within the next decade, the European Space 
Agency's JUpiter Icy Moon Explorer (JUICE) will travel to the Jovian moons, 
with the goal of evaluating the potential presence of habitable environments 
- primarily on Ganymede, Europa and Callisto, each of which are believed 
to contain a subterranean water ocean. The starting chemicals used in 
the shock synthesis study may be present on the surfaces of these icy 
satellites. Even with current data, scientists believe ammonia, at least, 
is present as a "volatile ice" in the crusts of Ganymede and Callisto. 

With the unprecedented resolution JUICE will provide, researchers might, 
in the not too distant future, be in a position to see whether the countless, 
unseen collisions with these alien worlds left something more than craters 
and dust.