Hit-and-Run Collision – no reported injuries

So, here are some of the highlights we picked from the MetSoc program during our recent lunchtime meeting. (If some of the terms are a bit confusing have a look in the “Jargon Buster” section for a more detailed explanation).

Kicking things off on the first morning of the conference, there is a session on iron meteorites. These lumps of metal are thought to be fragments from the cores of asteroids. One outstanding problem is what happened to all the surrounding rocky material? This seems to be largely absent from our meteorite collections. One possibility is that these asteroids were destroyed early in the history of the Solar System, during so-called hit-and-run collisions. In these events, the outer silicate part was mostly destroyed, but the tough metal core survived.

Also on the first day, there is a session looking at organic material in meteorites. The origin of this component remains controversial. In particular, the role of processes taking place in interstellar space, compared to those on asteroids and comets, is much debated.

Further results from the NASA Stardust mission will also be presented at the meeting. Fragments from the comet Wild2, trapped in a substance called aerogel, continue to produce exciting discoveries. In particular, the presence of chondrules, similar to those seen in certain meteorites, suggests that asteroids and comets may not be as different as was once thought.

One of my favourite picks comes from the session looking at asteroids. The so called ordinary chondrites are by far the most common type of meteorite arriving on Earth, making up about 80% of all falls. They are currently split into five groups and so should come from at least five different asteroids. At present, only one asteroid has been positively identified as a source for the ordinary chondrites that arrive on Earth. Where are the others? More research work needed, it seems.

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