Studying the surfaces of the Moon and Mercury has allowed us to understand how t
ID: 235001 • Letter: S
Question
Studying the surfaces of the Moon and Mercury has allowed us to understand how the amount of debris in the solar system that can impact planetary surfaces has varied over time. In general, the rate of cratering on these bodies
shows that large asteroid impacts are more common now than in the past.
has remained constant over the last 4.6 billion years.
has recently increased with more collisions in the asteroid belt.
shows that most interplanetary debris was swept up soon after the formation of the solar system.
fluctuates over time, with massive bodies occasionally coming in from the Oort Cloud.
shows that large asteroid impacts are more common now than in the past.
Explanation / Answer
The standard theory of solar system origin is that it formed from the collapse of a gas cloud containing a small amount of dust. Most of the material fell to the center to form the sun and the remaining material flattened into a swirling orbiting disk. Through some unknown process, matter within the disk began to coalesce into larger particles and these planetesimals eventually grew in size until some of them were large enough that their gravity attracted most of the planetesimals near their orbits to form into planets. Remaining material formed into satellites (moons) of the planets, minor planets (asteroids), and comets. Once the terrestrial planets, satellites, and minor planets had formed and cooled so that they had solid surfaces, their gravity continued to assist them in accumulating remaining planetesimals.Astronomers call this episode the Early Heavy Bombardment (EHB) that continued until about 4.1 billion years ago. Between 4.1 and 3.8 billion years ago was the Late Heavy Bombardment (LHB) when very large and intense cratering occurred. After the LHB, the cratering rate greatly reduced to nearly the slow rate that we have today. The distinction between the EHB and LHB was required because of the fact that many large impact basins appear to have formed on the moon very late. This paradigm of interpreting craters on the moon has been imposed upon the rest of the solar system.This indicates that most interplanetary debris was swept up soon after the formation of the solar system.