Late and heavy: Did a fifth rocky planet, long subsumed by the Sun, create the bombardment that pockmarked the surface of the Moon?
Credit: NASA
NEW YORK: The fiery demise of a fifth rocky planet in our Solar System might have led to a flurry of asteroid impacts that pockmarked the Moon and Earth billions of years ago.
The Late Heavy Bombardment (LHB) is a relatively brief period, about 3.9 billion years ago, when wayward space projectiles heavily pelted the Moon and inner planets. Craters from that chaotic time are still visible on the Moon, but have been erased from Earth, where the crust is continually recycled.
All shook up
Try as they might, astronomers have not yet been able to pin down a cause for the bombardment. Some experts have postulated that a shuffling up of the arrangement of the planets in their youth may have been responsible. One popular theory is that the outward migration of a young Neptune perturbed rocky bodies in the distant Kuiper Belt, causing some to veer into the inner Solar System.
But John Chambers, an astrophysicist at the Carnegie Institution in Washington DC, now says the size distribution of craters on the Moon better match asteroids from the Asteroid Belt, located beyond the orbit of Mars. And he thinks the misbehaviour of a long-lost, fifth rocky planet called 'Planet V' was the trigger that upset the gravitational balance of the belt and ejected some of its inhabitants. Our Solar System currently contains four rocky planets: Mercury, Venus, Earth and Mars.
Using a new computer model detailed in a recent issue of the journal Icarus, Chambers provides the most compelling evidence yet that a hypothetical Planet V could have existed for hundreds of millions of years before minute gravitational tugs from Mars and Jupiter destabilised its orbit, causing it to fall into the Sun.
"Before it was lost, its orbit would have moved across the Asteroid Belt for quite a long period of time, scattering asteroids as a result," Chambers said. "My model would predict that it's only asteroids, and not comets, that caused the impacts, and that the asteroids would tend to come from the inner asteroid belt."
Unknown planet
Planet V's orbit was between that of Mars and the Asteroid Belt, Chambers predicts, and it may have been smaller than Mars but larger than our Moon. "If it was bigger than Mars, then Mars should have been the one that was lost," he said. "If it's smaller than the Moon, that's not really big enough to disturb the Asteroid Belt much."
David Kring, a planetary scientist at the U.S. Lunar and Planetary Institute in Houston, Texas, agrees that the Planet V hypothesis is interesting because it suggests an inner Solar System origin for the impacting debris. But he added that Chamber's "model relies on the invention of an unknown planet... so it is a hypothesis that will need to be rigorously tested with the geologic record."
One such test could be done if scientists had more lunar rock samples, he said. It was using these samples, returned by NASA's Apollo missions, that scientists were able to date the Late Heavy Bombardment in the first place.
simple answers to complicated questions
If we all agree that the solar system formed just as we were taught; then how is it even possible for there to be an asteroid belt?
During planet formation swirling clouds absorbed all matter surrounding it and became a planet. The size of the planet depended on how much matter it absorbed.
So why was the asteroid belt not absorbed?
...
We all agree that at one point the Earth was warmer than it is now and had massive plant and animal growth, far larger then than now. Dinosaurs, giant reptiles would have needed to have far warmer climates to grow and survive as well as the abundance of then tropical plants world wide.
We all agree that at one time Mars had water. We can look at the terrain and determine that rivers flowed on the surface.
...
We all agree that every action has an equal and opposite reaction. Everyone knows how gravity works and how it affects the pull on planets.
...
We all agree there was a period where asteroids pummeled all the planets / rock planets that we can visibly see at any rate. The Earth, Mars, Mercury, and our moons.
...
Do the math. Place another planet between Mars and Jupiter and it would shift the planets in both directions as it would take up the space and displace the planets around it.
This would cause Earth and Mars to be closer to the Sun. That would explain the warmer temperature and the growth of reptiles as well as Mars having flowing water.
...
Now break that planet up and the opposite would occur. The planets would roll back and forth until they settled into a solid orbit again. Hence the mass extinction and ice age as well as Mars cooling. Global movement means plate shifts, ocean movement and rapid freezing all very sudden. It explains the impact craters on all the other rock planets and moons. It also explains why there is an asteroid belt floating between planets that should have been absorbed when they formed.
...
How or why the planet came apart? I have no clue, but everything else is easy to see. The assumption that somehow a stream of asteroids barreled along thru the solar system and just came into orbit is farfetched at best. If indeed a stream of object would have come through they would have been sucked into Jupiter’s gravitation pull, but the idea that they somehow snaked their way through all the other planets and just took up their current orbit? The explanation I give simply makes far more sense and explains how and why the other events came to be.
...
But that’s just what I know.
LL
i like
this cool pict