[meteorite-list] Space Weathering: Solar wind tans young asteroids

[Meteorites USA]

A while back I asked a question about what meteoroid and asteroids look 
like in space, specifically what color they were and in addition if any 
asteroids or meteroids might have fusion crust. The fusion crust part 
was answered nicely and produced a good discussion on earth grazers and 
hypotheses on how many might lie out there in our solar system. Yet I 
was still curious about the natural phenomena that ages asteroids and 
changes their color. While searching around I found these articles. A 
good read...

"Asteroids seem to get a 'sun tan' very quickly," said lead author 
Pierre Vernazza, "but not, as for people, from an overdose of the Sun's 
ultraviolet radiation, but from the effects of its powerful wind."

http://www.astronomy.com/asy/objects/images/asteroid-solar-wind.jpg

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April 23, 2009
A new study published in Nature this week reveals that asteroid surfaces 
age and redden faster than previously thought — in less than a million 
years, the blink of an eye for an asteroid. This study has confirmed 
that the solar wind is the most likely cause of rapid "space weathering" 
in asteroids. The result will help astronomers relate the appearance of 
an asteroid to its actual history and identify any after effects of a 
catastrophic impact with another asteroid.

Read the full article on Astronomy.com: 
http://www.astronomy.com/asy/default.aspx?c=a&id=8176 
<http://www.astronomy.com/asy/default.aspx?c=a&id=8176>
<http://www.upi.com/Science_News/2009/04/23/Solar-wind-found-to-age-asteroid-surfaces/UPI-12581240511504/>

PARIS, April 23 (UPI) -- A European Space Agency-led team of astronomers 
has determined the rapid space weathering seen on asteroid surfaces is 
most likely caused by the solar wind.

The study led by ESA scientist Pierre Vernazza reveals that solar wind 
ages and reddens asteroid surfaces much more quickly than previously 
thought -- in less than a million years. The scientists said their 
finding will help astronomers relate the appearance of an asteroid to 
its actual history and identify any after effects of a catastrophic 
impact with another asteroid.

It has long been known that asteroid surfaces alter in appearance with 
time, but the actual processes of the "space weathering" and the 
timescales involved were controversial.

The new study -- using the European Southern Observatory's New 
Technology Telescope and the Very Large Telescope, both in Chile, as 
well as telescopes in Spain and Hawaii -- solved the puzzle.

When two asteroids collide, they create a family of fragments with 
"fresh" surfaces, the researchers said. The astronomers found that newly 
exposed surfaces are quickly altered and change color in less than a 
million years -- a very short time compared to the age of the solar system.

The research that included Richard Binzel of the Massachusetts Institute 
of Technology, Alessandro Rossi of Italy's Institute of Information 
Science and Technologies and Marcello Fulchignoni and Mirel Birlan, both 
of the Paris Observatory, appears in the journal Nature. SOURCE: 
http://www.upi.com/Science_News/2009/04/23/Solar-wind-found-to-age-asteroid-surfaces/UPI-12581240511504/



-- 
Regards,
Eric Wichman
Meteorites USA
http://www.meteoritesusa.com
904-236-5394