Blogs / Bad Astronomy

1) The new Carnival of Space is up at Lab Lemming’s tent, and it’s a BIG tent.

2) Emily has news that Phobos is a bit lighter than previously thought. What a pile.

3) Emily also has some nifty new MESSENGER images explained. I’ve been too lazy to deal with that.

4) Tom notes that HiRISE spotted Spirit on Mars. Massively embiggenated version is here.

4) This is dumb. So why did it make me smile so much? Oh right: I’m a dork.

The instant I saw the avalanche image from the HiRISE camera on-board MRO orbiting Mars, I knew I would have a contender for my Top Ten Astronomy Pictures of 2008.

But then they released this one at the same time:

Yeah, that’s us. That’s home. We were 192 million kilometers (115 million miles) from Mars when HiRISE turned around and took this picture. Right away I could tell that was South America’s west coastline… which is incredible. I also was just starting to wonder about the Moon in the image when I read that it had been brightened artificially to make it easier to see; in general the Earth is 3-4 times more reflective than the Moon, so it’s a lot brighter.

The Mars-Earth-Sun angle was just about 90 degrees when this was taken, which is why the Earth and Moon are half-full. Note that in reality, the Moon is about 30 Earth-diameters away from the Earth, so we’re seeing some perspective here. The Moon was a day before third quarter when this was taken, so it was actually a bit closer to Mars than the Earth was when HiRISE snapped this picture.

Beautiful.

This is TOTALLY HAWESOME: an avalanche on Mars was caught in the act by the HiRISE camera.

This picture shows the billowing dust cloud from an avalanche of ice and dust along scarps — sheer cliffs — near the north pole of Mars. To give you a sense of scale, the cloud is about 180 meters across, and about the same distance from the base of the cliff.

Holy cow.

You can see the cliff in the middle of the picture. It’s 700 meters high (2300 feet!) and slopes at about 60 degrees; that’s pretty close to vertical. To the left you can see white carbon-dioxide frost (which is evaporating as spring ensues in the Martian northern hemisphere) at the top of the cliff.

If my (very) rough calculations are accurate, it would take a rock about 20 seconds to fall from the top of the cliff, and would hit the bottom at about 70 meters/second, or about 150 miles per hour. Look out below!

You can read lots more about this on the HiRISE page.

Sidenote: after the disappointing news from HiRISE this weekend, I feel a lot better about this. Totally amazing. I might even say ground breaking.

Update: The HiRISE blog has a more personal take on this as well.