[meteorite-list] 'Cosmic Botox' Bashes Asteroid Wrinkles Away (Eros)

From: Dawn & Gerald Flaherty <grf2_at_meteoritecentral.com>
Date: Wed Jul 20 21:02:24 2005
Message-ID: <02af01c58d8f$d3ca2fd0$6502a8c0_at_GerryLaptop>

Wow, that's an impressive supposition. Jerry
----- Original Message -----
From: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>
Sent: Wednesday, July 20, 2005 6:38 PM
Subject: [meteorite-list] 'Cosmic Botox' Bashes Asteroid Wrinkles Away
(Eros)


>
>
> http://www.newscientist.com/article.ns?id=dn7699
>
> 'Cosmic Botox' bashes asteroid wrinkles away
> Zeeya Merali
> 20 July 2005
>
> Meteoroid impacts can give facelifts to asteroids, knocking hundreds of
> millions of years off their apparent age. The finding casts doubt on the
> reliability of current asteroid dating methods.
>
> The only way to date most asteroids, like other bodies in the solar
> system, is to infer their ages from the number and appearance of craters
> that pockmark their surfaces. Heavily cratered objects suggest ancient
> surfaces that have long been pummelled by space rocks. The only
> exception to the rule is the asteroid Vesta, which has been dated
> radiometrically using meteorites known to have originated there.
>
> But a new Nature study by Peter Thomas of Cornell University in Ithaca,
> New York, and Mark Robinson of Northwestern University in Evanston,
> Illinois, both in the US, hints the crater-based technique may not
> always be accurate.
>
> They mapped the craters on the 33-kilometre-long asteroid Eros using
> more than 100,000 images taken by NASA's NEAR Shoemaker spacecraft
> between 2000 and 2001. They noticed that 40% of the asteroid's rocky
> surface bore far fewer craters than the rest of it.
>
> Smooth and youthful
>
> At first Thomas thought that a meteoroid impact might have created a
> massive crater. That would have thrown debris into the air, which then
> could have blanketed small craters in the area. "But there clearly
> wasn't enough material in the central crash site to fill so many holes
> by that process," he explains.
>
> Now he believes a collision with a meteoroid a few hundred metres across
> caused an asteroid-quake on Eros, which appears to be coated in 100
> metres of soil-like regolith. The seismic waves set Eros shaking so hard
> that the smallest craters within a 9 km radius of the crash site
> collapsed, he suggests, giving it a smoother, more youthful appearance.
>
> "One impact can completely re-set a surface," says Thomas. "If you only
> look at part of an asteroid's surface, instead of at the whole thing,
> you could be fooled into thinking it's a factor of 10 younger than it is."
>
> Erik Asphaug, a planetary scientist at the University of California in
> Santa Cruz, US, agrees. "This asteroidal Botox calls into question the
> habit of dating asteroid surfaces through their cratering record," he
> writes in an accompanying article.
>
> Journal reference: Nature (vol 436, p 335, 364)
>
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Received on Wed 20 Jul 2005 09:02:11 PM PDT