Earth-Venus smash-up possible
Pastor Dale Morgan
Earth-Venus smash-up possible*
From correspondents in Paris
Agence France-Presse
June 11, 2009 04:37am
A FORCE known as orbital chaos may cause our solar system to go haywire,
leading to a possible collision between earth and Venus or Mars,
according to a study released today.
The good news is that the likelihood of such a smash-up is small, around
one-in-2500.
And even if the planets did careen into one another, it would not happen
before another 3.5 billion years.
Indeed, there is a 99 per cent chance that the sun's posse of planets
will continue to circle in an orderly pattern throughout the expected
life span of our life-giving star, another five billion years, the study
found.
After that, the sun will likely expand into a red giant, engulfing earth
and its other inner planets - Mercury, Venus and Mars - in the process.
Astronomers have long been able to calculate the movement of planets
with great accuracy hundreds, even thousands of years in advance. This
is how eclipses have been predicted.
But peering further into the future of celestial mechanics with
exactitude is still beyond our reach, said Jacques Laskar, a researcher
at the Observatoire de Paris and lead author of the study.
"The most precise long-term solutions for the orbital motion of the
solar system are not valid over more than a few tens of millions of
years," he said.
Using powerful computers, Mr Laskar and colleague Mickael Gastineau
generated numerical simulations of orbital instability over the next
five billion years.
Unlike previous models, they took into account Albert Einstein's theory
of general relativity. Over a short time span, this made little
difference, but over the long haul it resulted in dramatically different
orbital paths.
The researchers looked at 2501 possible scenarios, 25 of which ended
with a severely disrupted solar system.
"There is one scenario in which Mars passes very close to earth," 794
kilometres to be exact, said Mr Laskar.
"When you come that close, it is almost the same as a collision because
the planets get torn apart."
Life on earth, if there still were any, would almost certainly cease to
exist.
To get a more fine-grained view of how this might unfold, Mr Laskar and
Mr Gastineau ran an additional 200 computer models, slightly changing
the path of Mars each time.
All but five of them ended in a two-way collision involving the sun,
earth, Mercury, Venus or Mars. A quarter of them saw earth smashed to
pieces.
The key to all the scenarios of extreme orbital chaos was the rock
closest to the sun, found the study, published in the British journal
Nature.
"Mercury is the trigger, and would be be the first planet to be
destabilised because it has the smallest mass," said Mr Laskar.
At some point Mercury's orbit would get into resonance with that of
Jupiter, throwing the smaller orb even more out of kilter, he said.
Once this happens, the so-called "angular momentum" from the much larger
Jupiter would wreak havoc on the other inner planets' orbits too.
"The simulations indicate that Mercury, in spite of its diminutive size,
poses the greatest risk to our present order," said University of
California scientist Gregory Laughlin in a commentary, also published in
Nature.