SETI bioastro: Are 75% of all Earth-type worlds 0.9 to 2.7 billion years older than our planet?

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From: Larry Klaes (
Date: Thu May 31 2001 - 13:41:24 PDT

From: []On Behalf Of
Bruce Moomaw
Sent: Sunday, May 27, 2001 3:38 AM
Cc: Jupiter List; Icepick Europa Mailing List
Subject: May and June "Icarus" abstracts are in

It never rains but it pours; no sooner did the abstracts from the April
"Icarus" turn up belatedly on the Web than those for the May and June issues
turned up too (all of them apparently delayed by the journal's slow
reorganization of its own website):

Particularly interesting from May and June:

(1) A set of four May abstracts by Erich Karkoschka on the results of
Hubble's latest observations of Uranus, its rings and moons;

(2) A June piece proposing that the puzzling "Late Heavy Bombardment" --
the sudden storm of big impactors that seems to have rained down on the
inner planets after the initial bombardment had slackened off -- may have
been due to the late formation of Uranus and Neptune, which then diverted a
new wave of planetesimals from the outer Solar System into the inner one;

(3) A June near-IR compositional survey of near-Earth asteroids, which turn
out to be convincing sources for the ordinary-chondrite meteorites, but also
more varied than the larger Main Belt asteroids. (1989 ML -- the target for
Japan's MUSES-C sample return mission -- seems to have "a neutral spectrum
that may be interpreted as a shock-darkened ordinary chondrite.")

(4) A June piece by Charles Lineweaver, in which he sets forth an ingenious
(and, to me, rather convincing-sounding) argument that "3/4 of the
Earth-like planets in the Universe are older than the Earth, and that their
average age is 0.9 to 2.7 billion years older than the Earth."

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