[meteorite-list] New Theory: Catastrophe Created Mars' Moons

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:21:10 2004
Message-ID: <200307292027.NAA03854_at_zagami.jpl.nasa.gov>

http://space.com/scienceastronomy/mars_moons_origin_030729.html

New Theory: Catastrophe Created Mars' Moons
By Leonard David
space.com
29 July 2003

PASADENA, California - The two moons of Mars - Phobos and Deimos - could be
the byproducts of a breakup of a huge moon that once circled the red planet,
according to a new theory.

The capture of a large Martian satellite may have taken place during or
shortly after the formation of the planet, with Phobos and Deimos now the
surviving remnants.

Origin of the two moons presents a longstanding puzzle to which one
researcher proposed the new solution at the 6th International Conference on
Mars, held here last week.

"Nobody has been able to explain the origin of Phobos and Deimos," said S.
Fred Singer of the University of Virginia's Science & Environmental Policy
Project in Arlington, Virginia.

Violating laws

Based on research performed as a visiting scientist at the Lunar & Planetary
Institute in Houston in October 2002, Singer said that conventional
hypotheses about the moons either violate physical laws or have difficulty
accounting for their observed orbits.

Singer reported at the meeting that "there are no ready alternatives to
explain the origin of the Martian moons."

At present, both satellites have near-circular and near-equatorial orbits.

Phobos' orbit, however, has been observed to shrink since its discovery in
1877. The present track of Deimos -- just beyond the synchronous limit where
it nearly matches the spin rate of Mars - is an important data point, Singer
said.

"Is that by accident? I don't think so - it gives you a clue about its
origin," he told SPACE.com.

Through a complex set of orbital calculations involving Mars, the large
hypothetical Mars moon itself, and tracing back in time the past and present
whereabouts of Phobos and Deimos, Singer believes he has a case.

In the Singer scenario, the close proximity of a large original moon to the
red planet - captured in Mars synchronous orbit -- would have eventually
fractured the object. Gravitational pushes and tugs would have turned it
into a rubble pile that would still cling together gravitationally.

"Forces would soon drive the largest pieces into Mars, with the smallest
pieces remaining as Phobos and Deimos," Singer said. In the breakup process,
the most massive pieces would spiral in far more rapidly, crashing into the
planet. "We need to look for some sign that these existed."

Phobos: going, going, gone

A fundamental prediction by Singer is that the moons are similar in
composition and petrology. However, Phobos and Deimos do not appear to be
comparable. That distinction is obvious in looking at the differences in
their regoliths - each moon's topside covering.

"We need both surface and deep samples to decide this issue, and to
investigate whether Phobos and Deimos once formed as parts of a larger body,
most of which has now disappeared, perhaps by impacting on Mars," Singer
said.

Singer said Phobos will die in a few million years.

"We're lucky in the sense that we're seeing Phobos while it's still around,"
he said.

Destination Deimos

Singer has plans for Deimos.

The scientist believes the moon would serve as a natural space station for
future human explorers.

"First of all, humans on the surface of Mars cannot really do the
exploration directly. They have to use rovers to get around. To go from the
equator to a pole on Mars just takes too long. It's a big, dangerous
journey," Singer said.

What Singer envisions is a Deimos gateway to extensive Mars exploration. An
encampment of astronauts would reside on the Martian moon. From there,
dozens of rovers could be autopiloted, in real-time.

"There would be no time delay, or so short that it's within the human
reaction time," Singer said. From Deimos, quick, down-to-the-surface sorties
could be undertaken by humans to select areas, he added.

"This would be a 15-year project, as I look at it. It would cost roughly $30
billion, funded at some $2 billion a year average. That's well within the
existing NASA budget," Singer said.

On the political side, Congress is not likely to fund a long series of
robotic roving probes to Mars that extends over decades.

"That would not be a very efficient way of studying Mars. If you want to
solve the really big problems of Mars, like origin of life, you need to do
this in one fell swoop," Singer concluded.
Received on Tue 29 Jul 2003 04:27:02 PM PDT