[extropy-chat] stardust at home

Amara Graps amara at amara.com
Sat Jan 21 09:31:44 UTC 2006


>Hey this is cool: volunteers search thru a virtual
>microscope to identify cosmic dust impact regions

A reminder that you will not be searching the part of the aerogel that
was open during the comet Wild-2 flythrough, but the other side of the
aerogel that was open to interstellar dust. Information from the
Stardust web site said that the interstellar dust collection times
were from March-May 2000 and July-December 2002 (which I wrote it at
Wikipedia, and noone changed :-) )

>Amara may be able to verify, but it is easy to imagine that
>several tons of cosmic dust enter the atmosphere every

More, here are the details I know from the researchers -

Generally, an average of 40 tons per day of extraterrestrial material
falls to the Earth. Elmar Jessberger at the Institut fuer Planetologie
in Muenster and his colleagues estimate that most of the influx of
extraterrestrial matter onto the Earth is dominated by meteoroids with
diameters in the range 50 to 500 micrometers, of average density 2.0
gr/cm^3 (with porosity about 40%). George Flynn at SUNY-Plattsburgh,
who focuses his studies on the interstellar component of the
extraterrestrial dust, says that 20 kilograms of interstellar dust
particles, in the size range 0.3 to 1 micrometers and densities of 3
gr/cm^3, falls to the Earth over a period of about 2 months.  In
addition, models show that 20 percent of the Earth-falling dust in a
size range near 0.5 micrometers as interstellar in origin.

My Sky and Telescope article about cosmic dust

My Wikipedia pages about cosmic dust (obviously in progress)

By the way, I hope y'all know that there is a Student Dust Counter on
the Pluto New Horizons mission, just launched. It is the first NASA
student instrument, designed and built wholly by engineering students
at the University of Colorado, Boulder. My dust charging 'mentor'
Mihaly Horanyi was/is advising them on this project. It will be the
first dust collection in the outer solar system; the instrument will
be on in the inner solar system as well, so one can correlate that
data with other dust detectors that are flying and have flown in the
solar system.

>There is a fairly straightforward calculation that
>shows that a lifeform on a sufficiently small grain of
>cosmic dust could survive atmospheric reentry.  I will
>dig out the text on this, or perhaps attempt to rederive
>it from first principles, should there be sufficient
>replyage to this comment.

If you look up references by Mark J. Burchell and Gerda Horneck on
NASA ADS: http://adsabs.harvard.edu/abstract_service.html  then you
should find some good information, since it's the topic of much
of their research.

For example:







I should add that I was incredibly annoyed by the pre-Stardust capsule
return NASA TV coverage of the statements made by Don Yeomans (JPL):
"We wouldn't be here if it weren't for comets.."

... which I say is debatable, under study, and not proven!

- We don't know if a comet is the cause of the dinosaur extinction
  (if iridium is present in comets then the evidence is good)

- We don't know how much water comets carry 
(under study)

- We don't know how much water comets carried to Earth
(but probably less than 10% from isotopic studies).

-We don't know how much organic material comets carry
(but we are learning quickly)

-We don't know how much biotic material comets can carry
  (under study)

- We don't know how well biotic material can survive reentry into the
Earth's atmosphere
(under study)

I wish Yeomans didn't say these words, because the Italian media
jumped on it, and made it a large aspect of their reports.
("humans exist because of comets...") Grrrrrrrrrrrr



Amara Graps, PhD          email: amara at amara.com
Computational Physics     vita:  ftp://ftp.amara.com/pub/resume.txt
Multiplex Answers         URL:   http://www.amara.com/
"We came whirling out of Nothingness scattering stars like dust."

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