[meteorite-list] Earth Rocks Could Have Taken Life to Titan (doubts)

From: mark ford <markf_at_meteoritecentral.com>
Date: Tue Mar 21 22:16:34 2006
Message-ID: <6CE3EEEFE92F4B4085B0E086B2941B31508C72_at_s-southern01.s-southern.com>

Hi Mike,

Well I'm not an escape velocity so take this with a pinch of salt, but
when meteorite enters the atmosphere it will have a high 'cosmic
velocity' not just the Earth's gravitational attraction speed, so in
fact the speed of an incoming meteorite would be significantly faster
than just escape velocity alone, i.e more heating.

Therefore going the other way (escaping earth) would probably not be as
fierce as coming in. And of course the angle it was ejected at would
probably greatly alter the chances of it escaping or returning to Earth.

But remember there is a big difference between possible and probable, I
suspect that the odds are just way too high for Titan material transfer
let alone earth biological transfer - there is an awful lot of space and
other planets in between.

You can to break it down into:

Odds of any life still being present in the impact ejector and the
material surviving impact (unlikely)
Odds of the material making it into space (very rare)
Odds of the material escaping earths orbit (very very rare)
Odds of the material being flung at exactly the right direction and
velocity for Titan transfer (extremely rare)
Odds of the material surviving entry into Titans thick atmosphere (rare)
Odds of the material surviving impact (if it survives entry then
probably likely)
Odds of any biological material surviving in the material (unlikely -
very long cosmic age)
Odds of it actually being able to survive in the new climate (very
unlikely)

I say that any of those 'odds' would be enough to make it pretty much
not going to happen!

We don't even know for sure if there are any Earthites on earth let
alone earth rocks on other planets!

Just my 2g worth,

Mark Ford




-----Original Message-----
From: meteorite-list-bounces_at_meteoritecentral.com
[mailto:meteorite-list-bounces_at_meteoritecentral.com] On Behalf Of Mike
Fowler
Sent: Monday, March 20, 2006 5:18 PM
To: meteorite-list_at_meteoritecentral.com
Cc: Mike Fowler
Subject: [meteorite-list] Earth Rocks Could Have Taken Life to Titan
(doubts)

> He says only boulders at least 3 metres across could punch out through
> the Earth's atmosphere and escape the planet's gravity, and that only
> extremely powerful impacts could achieve this. The cause of such
> impacts
> would be comets or asteroids between 10 and 50 kilometres wide,
> Gladman
> told New Scientist: "The kind of thing that killed the dinosaurs."

I have my doubts. (again) Someone please correct me if I err in my
numbers or logic.

A rock being ejected into space is somewhat like a meteorite falling
to Earth, but in reverse.
To be ejected into space the rock must leave Earth's atmosphere with
escape velocity. That means, it must have been accelerated to a
velocity GREATER than escape velocity to account for the velocity
lost punching thru Earths atmosphere.

Question #1 Can an impact accelerate rocks greater than 3 meters in
diameter to 15 kilometers per second,or more, without shock melting
them, or pulverizing them?

Meteorites entering the Earth's atmosphere push ahead of them a
column of air until the pressure on the meteorite exceeds the
crushing strength of the meteorite, at which point it explodes and
the surviving pieces fall under the influence of gravity.

Question #2 If a whole rock, 3 meters or more in diameter, could be
accelerated to 15 kps intact, wouldn't the back pressure of the
atmosphere exceed the strength of the rock resulting in fragmentation
into pieces, just as happens to virtually all stony meteorites
passing thru the Earth's atmosphere with similar velocity? Such
pieces will not coast into space, on the contrary they will be
retarded by the remaining atmosphere, and quickly loose escape velocity.

I would never say something is impossible.

But I have my doubts about hundreds of millions of Earth Boulders
being ejected thru the atmosphere unless you can overcome the above 2
objections.

Any comments Sterling or others?

Mike Fowler
Chicago






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Received on Tue 21 Mar 2006 04:27:36 AM PST