Impact Craters

[thnkrx]

http://www.lpl.arizona.edu/impacteffects/<br /><br />Fun to muck about with.<br /><br />A lot of the smaller ones tend to breakup in the high atmosphere, creating debrie fields; this seems to be true even for objects moving at near relativistic velocities. <br /><br />Speaking of near relatavistic velocities, I tried a couple featuring `spaceship' sized masses hitting at around 80-90 psl...lets just say you wouldn't care to be on the same continent...or at least within a thousand kilometers.

 

[bdewoody]

From looking at images of Mercury, our moon and other rocky moons that asteroids and comets come at us from all angles. One would think that they would strike predominantly along the general plane that the planets lie in but after looking at the Mercury images it is apparent that we can be struck from any angle. So, in the search for NEO's are they looking in all directions? <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[MeteorWayne]

In interesting question with some complicated answers.<br /><br />First, you are assuming that because most of the craters are round, that the impact muct have come from that direction. It turns out that is not the case. I forget the exact angle, but it has been shown that except for very shallow angles (< 15 degrees?) the resultant crater will be round, so you can't tell what direction the impactor came from.<br /><br />While it is true that 98% of the material in the solar system is prograde (goes around the sun in the same direction as the earth), especially for the small solar system bodies the inclination (angle relative to the plane of the solar system) is not very tightly constrained.<br /><br />For example, see this image which shows the loaction of bodies in the inner solar system. (Note, for some reason that link is down, when it comes back I'll add it)<br /><br />Instead see this histogram of the inclination of objects.<br />You can see there are quite a few that have high enough angles to impact anywhere on any object, especially near the focus of the elliptical orbits; i.e. the inner solar system.<br /><br />Finally, yes they are looking in all directions. However, they are looking more often near the plane of the solar system since that's where the most objects are.<br />Unfortunately, with limited money, you tend to look where you will get the most results, i.e. new objects. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>