The fifth planet??

[Ronn! Blankenship]

Long-Destroyed Fifth Planet May Have Caused Lunar Cataclysm, Researchers Say

By Leonard David Senior Space Writer
posted: 03:00 pm ET 18 March 2002

http://www.space.com/scienceastronomy/solarsystem/fifth_planet_020318.html

HOUSTON, TEXAS -- Our solar system may have had a fifth terrestrial planet, one
that was swallowed up by the Sun. But before it was destroyed, the now missing-
in-action world made a mess of things.

Space scientists John Chambers and Jack Lissauer of NASA's Ames Research Center
hypothesize that along with Mercury, Venus, Earth, and Mars -- the terrestrial,
rocky planets -- there was a fifth terrestrial world, likely just outside of
Mars's orbit and before the inner asteroid belt.

Moreover, Planet V was a troublemaker.

The computer modeling findings of Chambers and Lissauer were presented during
the 33rd Lunar and Planetary Science Conference, held here March 11-15, and
sponsored by NASA and the Lunar and Planetary Institute.

It is commonly believed that during the formative years of our solar system,
between 3.8 billion and 4 billion years ago, the Moon and Earth took a pounding
from space debris. However, there is an on-going debate as to whether or not
the bruising impacts tailed off 3.8 billion year ago or if there was a sudden
increase - a "spike" -- in the impact rate around 3.9 billion years ago, with
quiet periods before and afterwards?

This epoch of time is tagged as the "lunar cataclysm" - also a wakeup call on
the cosmological clock when the first evidence of life is believed to have
appeared on Earth.

The great cover-up

Having a swarm of objects clobbering the Moon in a narrow point of time would
have resurfaced most of our celestial next door neighbor, covering up its early
history. Being that the Moon is so small, Earth would have been on the
receiving end of any destructive deluge too.

Moon-walking astronauts brought back a cache of lunar material. Later analysis
showed that virtually all impact rocks in the "Apollo collection" sported
nearly the same age, 3.9 billion years, and none were older. But some
scientists claim that these samples were "biased", as they came from a small
area of the Moon, and are the result of a localized pummeling, not some lunar
big bang.

There is a problem in having a "spike" in the lunar cratering rate.

That scenario is tough to devise. Things should have been settling down,
according to solar system creation experts. Having chunks of stuff come zipping
along some hundreds of millions of years later out of nowhere and create a
lunar late heavy bombardment is a puzzler.

If real, what were these bodies, and where were they before they scuffed up the
Moon big time? The answer, according to Chambers and Lissauer, might be tied to
the the Planet V hypothesis.

"The extra planet formed on a low-eccentricity orbit that was long-lived, but
unstable," Chambers reported. About 3.9 billion years ago, Planet V was
perturbed by gravitational interactions with the other inner planets. It was
tossed onto a highly eccentric orbit that crossed the inner asteroid belt, a
reservoir of material much larger than it is today.

Planet V's close encounters with the inner belt of asteroids stirred up a large
fraction of those bodies, scattering them about. The perturbed asteroids
evolved into Mars crossing orbits, and temporarily enhanced the population of
bodies on Earth-crossing orbits, and also increased the lunar impact rate.

After doing its destabilizing deeds, Planet V was lost too, most likely
spinning into the Sun, the NASA team reported.

The temporary existence of more than 4 planet-sized bodies in the inner Solar
System is consistent with the currently favored model for the formation of the
Moon. Work by Chambers and Lissauer also supports the view that our Moon is a
leftover of a massive collision between Earth and a Mars-sized body 50 million
to 100 million years after the formation of the Solar System.

Striking view

Wendell Mendell, a planetary scientist here at NASA's Johnson Space Center,
said the new theory is intriguing.

"This idea and others within the last few years show that the Solar System is
filled with all sorts of gravitational resonances...that a lot of potential
orbits in the Solar System are chaotic and unstable," Mendell told SPACE.com.
"My sense is that this is a new idea. It's another thing to throw into the pot
that's not totally crazy."

The work suggests there's a match up in timing, Mendell said, with asteroids
striking the Moon and causing the effects that are seen in the dating of Apollo
lunar rocks.

"By thinking that the Solar System was really quite different in a major way
with an extra inner planet, we might be able to develop some sort of self-
consistent scenario that explains a lot of things. But all this is at the very
early stages now," Mendell said.

"We're moving into a really new regime," Mendell added, "where the Solar System
is not a static dynamic place from day one to now. It really might have had
some nuances and synchronicities associated with it that we have not really
tried to exploit before."

It takes a drill hole Setting the early Solar System and lunar history record
straight means going back to the Moon.

"The Moon is still the keystone to our understanding of the Solar System,"
NASA's Mendell said.

That too is the view of Apollo 17 astronaut, Harrison "Jack" Schmitt. Getting
back to the Moon to sort out the real story is a must, he said.

"You're going to have to be very, very specific on what sites you go to collect
new samples," Schmitt told SPACE.com. "It may be very difficult to
get an answer without using missions to fairly large impact craters that
penetrate through the ejecta. Those impacts are sort of a drill hole into the
lunar crust," he said.

Dating service

Places on the Moon where older, large basins have deposited ejecta are ideal
research zones, Schmitt said. Digging into such sites could yield
impact glass formed by basins perhaps dating older than 3.9 billion years old,
he said.

Just taking spot samples -- say from the Moon's South Pole Aitken basin --
could be risky, in terms of uncovering the Moon's rocky history,
Schmitt said. Such a huge area would take multiple robotic or human exploration
missions, each with significant roving abilities.

Also known as the "Big Backside Basin," Aitken is the largest impact crater on
the Moon, and one of the biggest in the Solar System.

For the near term, sets of low-cost, mini-robotic landers carrying specialized
gear would be ideal in opening up the Moon to further exploration, Schmitt
said.

"Numbers of targeted missions could get a lot of great information on some of
these fundamental questions that we still haven't been able to answer," Schmitt
said.

Getting back to the Moon with a settlement for resource exploitation is another
step forward. From such a site, human explorers can survey various lunar
locales - even the Moon's side that we Earthlings never see, Schmitt said.
"Then we can do the kind of thing that Apollo did for the near side of the
Moon," he said.




--Ronn! :)

I always knew that I would see the first man on the Moon.
I never dreamed that I would see the last.
--Dr. Jerry Pournelle


_______________________________________________
http://www.mccmedia.com/mailman/listinfo/brin-l