Saturn hovers over Mercury


As Murphy would have it, we’ve had heavy clouds and rain this week, so we weren’t able to look for Comet ISON.  The clouds finally blew away this morning, so we braved the cold morning to see if we could spot the comet through the colors of the sunrise.  We didn’t spot the comet, but we did see Saturn hovering above Mercury.  It was quite striking, don’t you think?

Rocks from Space!


A number of years ago, during a visit to Texas Christian University, I visited the Oscar Monnig meteorite collection.

Before this visit, I knew what meteorites were (rocks from space that actually make it to the Earth’s surface), but I had never given much thought to where they came from (other than the famous Mars meteorite).

Scientists, of course, had thought about it and have figured out the “parent” source of some meteorites.

A few meteorites have been caught on camera as they heat up falling through the Earth’s atmosphere, and their previous orbits can be determined from that data.  The results show that most meteorites came from the asteroid belt.

An early example is here:

Some clever scientists set up their cameras where it would be easy to find any meteorites that made it to the Earth.

Radar data can also be used to find meteorites and figure out where they came from.

But meteorites that are caught on camera during reentry are rare.

Scientists can also measure the reflection spectra of meteorites (the amount of light reflected back at various frequencies) and compare them to the telescopic spectra of various asteroids.  They found some pretty close matches:

But not all meteorites come from asteroids.  Some come from planets.

Martian meteorites tend to be “young” and contain gases that match the Martian atmosphere measured by the Viking spacecraft.

Lunar meteorites are also identified by their mineralogy and chemistry.

Recently, a meteorite was found in Africa that might originally be from Mercury:

How cool is that?