Frank wrote:My question is whether scientists can tell how old an object is from looking at it and inspecting the number of "hits". Is this an emperical judgement or is it an experienced guess?
I think its fairly obvious that if you start with an uncratered surface and objects hit it now and again, the number of visible imact craters increases over time. An uncratered surface has been recently altered and a highly cratered surface has been around for a long time without being altered.
Io has few craters and we have observed the active vulcanism which continuously remakes Io's surface. Its surface is geologically young. The Moon has lots of craters and a few areas which were smoothed over by volcanism in the ancient past. It is still a relatively old surface.
I would presume most of the objects in our solar system are the same age or the same age as the creation of the system. Presumably there could be objects that have been "captured" from outer space when they wandered into our sun's gravitational field.
Something asteroid sized could have been "created" relatively recently from the breakup of a larger body due to tidal forces or a catastrophic impact. It cold have a relatively "young" surface.
We're really talking about the age of the surface. But it follows that if you have a very old surface, you have a very old object.
[quote="Frank"]My question is whether scientists can tell how old an object is from looking at it and inspecting the number of "hits". Is this an emperical judgement or is it an experienced guess?[/quote]
I think its fairly obvious that if you start with an uncratered surface and objects hit it now and again, the number of visible imact craters increases over time. An uncratered surface has been recently altered and a highly cratered surface has been around for a long time without being altered.
Io has few craters and we have observed the active vulcanism which continuously remakes Io's surface. Its surface is geologically young. The Moon has lots of craters and a few areas which were smoothed over by volcanism in the ancient past. It is still a relatively old surface.
[quote]I would presume most of the objects in our solar system are the same age or the same age as the creation of the system. Presumably there could be objects that have been "captured" from outer space when they wandered into our sun's gravitational field.[/quote]
Something asteroid sized could have been "created" relatively recently from the breakup of a larger body due to tidal forces or a catastrophic impact. It cold have a relatively "young" surface.
We're really talking about the age of the surface. But it follows that if you have a very old surface, you have a very old object.