Blogs / Bad Astronomy

The Skeptics Circle #49 is now up at Autism Street, and it is very, very cool. I don’t have an entry in it this time (too much real astronomy and self-promotion the past two weeks to do much skeptical posting) but you just need to go see what Autism Street’s done. It’s excellent.

Also, the Philosophia Naturalis science blog carnival is up too, and I do have one there.

And as usual, vote for me! A vote for PZ Myers is a vote for the cephalapodufascist horde.

Note added at 18:38 Pacific: The Shuttle launch was scrubbed tonight due to weather. They will try again tomorrow (though the weather doesn’t look any better for then). Also, to the subject of the post below, I’m currently slightly ahead of PZ in the voting, but he has decided to go negative. I would never stoop to such things, obviously. I may have more on this development on Friday.

I’m so shameless.

Vote for me!

Or vote for one of the other extremely good science blogs. Or better yet, just vote for me. PZ already has three times my readership, and he gets angrier at creationists than I do, so he’s got a huge advantage. However — and really, I just hate to bring this up — he also has a rather unhealthy fascination with invertebrates (one which I have carefully helped cultivate in order to crush him in just such a situation as this). Really, what would Rick Santorum say?

From what I understand, you can vote once per day. Voting ends December 15, so get in there and vote for someone!

Just make sure it’s me.

I mentioned yesterday that besides water, the other interesting news from Mars Global Surveyor (MGS) is that they spotted lots of new craters, too (a crater in a new image was not in an older one). This allowed the scientists to determine the rate at which new craters are made, and they found that craters are created at a rate of about one per month. These aren’t dinky ones either– one they showed was the size of a football stadium!

Here’s a before-and-after shot of a new crater in Arabia Terra in Mars’ northern hemisphere:

It was created some time between January 1, 2004 and February 22, 2006. You can see the impact debris (what we astronomers in the know call "ejecta") spread out over an area a kilometer across.

The MGS team also mentioned that if you lived on Mars for about 20 years, on average you’d be close enough to one impact to actually hear it. Given that NASA plans on sending humans to Mars, this is a matter of real concern! It’s a tough problem– these are rocks that are maybe a few meters across, and so there is almost way to detect them. I have no idea how you could reliably find a large enough number of these potential impactors to do anything about them, and you really don’t want one touching down near a settlement.

Anyway for more detail and some cool images, go to Emily’s Planetary Society blog. She’s an actual planetary scientist and has more intelligent things to say about this than I do (you can also see the original images on the Malin Space Science Systems site. Emily also has a statement by the Planetary Society about what all this means for us as humans. It’s a good read.

STS-116 is scheduled for launch at 9:35 Eastern time on Thursday (for those of you who don’t read blog post titles). This is a mission to the space station (they all will be except for the one to Hubble in 2008). The weather may scrub the launch for now, with only a 40% chance of launch.

Still, if it goes off, it’ll be a night launch, which is cool. The one Shuttle launch I have seen — which lifted a camera I worked on for Hubble — was at 3:00 a.m. and it was spectacular. BABloggee Daniel Crawford let me know that this launch tonight (if it launches on time) should be viewable all up and down the east coast of the US. He also told me this launch is similar to one that happened in September 1997 when the Shuttle met up with the Mir space station. Back then, some timings were posted to a satellite observers group. The launch trajectory for this mission does look pretty similar, so I’m thinking the timings should be pretty close.

If you want to see the Shuttle on its way up, check that page and make sure you get out a few minutes before the time it says, just to make sure — in other words, immediately after launch. The page gives the time in minutes after launch you can see it at its highest from your location, that height above the horizon in degrees, and the azimuth (0 = north, 90 = east, 180 = south, 270 = west). For most of those locations, the Shuttle will be pretty low to the horizon, and towards the southeast. Make sure you have a clear horizon in that direction or you’ll miss it.

Again, the mission has a pretty big chance of being scrubbed, so keep your ears open for the news.

… but I’d better win.

The 2006 Weblog Awards nominations are official, and Bad Astronomy is on it! Woohoo! Unfortunately, the committee in charge of nominations somehow let in a bunch of clearly inferior blogs:

Pharyngula
John Hawks Anthropology Weblog
RealClimate
Deltoid
Good Math, Bad Math
Mixing Memory
The Panda’s Thumb
In the Pipeline
SciGuy

What the heck is a Pharyngula? Some people will do anything to get their blog noticed.

Voting begins tomorrow! So vote early and often.

Today at 10:00 a.m. Pacific time, NASA announced they had, at long last, found strong evidence of recent liquid water flows on Mars.

Observations from the Mars Global Surveyor (MGS) have revealed "recent activity" on the surface of the red planet; recent meaning in the past seven years. These changes include cratering from impacts (which is cool enough, and I’ll blog about those later), but also, yes, the flow of water.

Years ago, there were gullies seen on slopes on Mars, and they looked a lot like water had formed them. But it was hard to tell. Now, the evidence is far stronger. For example, check out this image:

This gully is in a crater in the Centauri Montes Region in the martian southern hemisphere. The critical piece of information here is that the gully did not exist light-toned features in the gully were not there in 1999, but are clear in 2005. It’s new!

In the higher resolution images (click it to see them) you can see the gully better. You can tell by eye it certainly looks like a liquid flow.

But how do we know they are water? The context is the key. Gullies indicate the flow of a liquid. Dust avalanches do occur on Mars, but not anywhere near these gullies. The morphology (shape) is important too. See how the gully breaks up as it flows down the slope? That also indicates a fluid flow. Finally, the color is an indicator, too. The light color is difficult to make on Mars. In trenches, most places where the surface dust is disturbed, and impact craters, the underlying layers are always almost always dark. This indicates a different process. Also, numerical calculations using models indicate that whatever caused these gullies flowed like water, not like dust or rocks.

As they say on the Malin Space Science Systems website:

Of course, water was not the only fluid considered by various colleagues; carbon dioxide can be fluid at some pressures and temperatures, and fluid carbon dioxide was also proposed as a candidate fluidizing agent. Even dry mass movement—landsliding—of unconsolidated granular material can exhibit some fluid-like behavior, and such mass movements were considered as an explanation for the gullies.

The presence of channels, primarily formed by erosion—but also displaying features representing along-channel deposition, such as levees and meanders—and terminal depositional aprons consisting of dozens to hundreds of individual flow lobes, contributed to the general acceptance of the hypothesis that gullies involved the action of liquid water.

These bright features in the gullies might be frost, but they’ve been around a while, so that’s pretty unlikely. They might be salts and other minerals deposited by the flow, or they might be smaller sediments carried along with the water.

How much water are we talking about? Maybe 5-10 swimming pools’ worth according to Ken Edgett, the scientist who has been working on these data. It would be a pretty quick flash flood, and, weirdly, in the low atmospheric pressure, the water would be boiling even at the low temperatures of Mars.

So what does this mean? Well, we’ve known of frozen water on Mars for decades, and we know there was activity in the past. These new observations indicate that things are happening on Mars now, within the past few years. And whatever it is that’s happening, it’s releasing water onto the surface, which in turn means that there is water just below the surface of Mars, at least in some places.

Sounds like a good place to build a colony, don’t you think?

It does to me. If there are big deposits of water, then that makes it a lot easier for potential colonists to survive on Mars, "living off the land". While the amount of water in any one gully is small, it indicates more water is nearby. This is terribly exciting.

Now, the skeptic in me must say it: this is not absolute conclusive proof of water on Mars. We need better images (maybe from the new probe orbiting Mars now), and spectra would be nice (to be able to see what chemicals are there). Even better would be to land a rover near there to get samples, though gullies down the sides of crater walls would make a perilous journey for any robot.

If these aren’t water gullies, we’ll all be disappointed, but that’s science. They’ll still be interesting features! But the evidence is very, very compelling, and I certainly hope that NASA follow this up quickly with more observations.

Recent flow of water on Mars from subsurface deposits. Wow.

Note added Wednesday night, 12/06: I made a couple of wording changes above due to some comments below. I checked, and the commenters were correct, so I made the edits. Thanks!

Note: At 10:00 a.m. Wednesday morning, NASA will be having a "major" press conference about Mars. All they have said is that it’s news from the Mars Global Surveyor, the probe with which they recently lost communication. The news is about something MGS found, and the rumor mill is grinding away. I know nothing more about this and wouldn’t break the embargo even if I did know. I’ll post after the conference. Until then, here’s an almost totally different topic.

I got an email from a friend the other day reminded me of something I did recently.

A couple of years ago, The Little Astronomer’s teacher asked if I could come in and give a talk to her 3rd grade class. I freaked about it, because I’m not used to talking to little kids. I emailed a friend who works at a museum and asked what she usually did, and she recommended I make a scale model of the solar system using a 100 foot rope.

Brilliant!

I put together a brief slide show of the planets, and prepared the rope. In the class, I gave them a tour of the solar system, then brought the kids outside. Once there, I got two kids each to volunteer to be a planet: one to hold the rope at the proper distance, and the other to hold a printout of a picture of the planet.

This worked fabulously. The inner four planets were pretty crowded, but after that things get space out (har har). Pluto is so far away that they really got to see and feel how big the solar system is, and why it takes so long for rockets to get to the planets.

My demo was a variation on a theme; it’s been done before. These kinds of scale models are terrific for kids: they’re fun, and anything hands-on is a lot better for the wee ones (and for the big kids like me, too, for that matter).

But back to my original thought here, the friend who emailed me was telling me about a scale model of the solar system on the Washington DC Mall. It looks pretty cool, and gives weary tourists a place to rest a moment between museums and yet still learn something.

It turns out the exhibit can be purchased for your local community. It ain’t cheap: at $160,000 a pop, you may need to get some donors for it. The product is the brainchild of the National Center for Earth and Space Science Education, which I think is a non-profit (they are sponsored by another umbrella organization).

Here’s how they describe the exhibit:

The Voyage exhibition is a one to 10-billion scale model of the Solar System stretching 2,000 feet (600 meters), and containing ten 8.5 -foot high aluminum stanchions locating the Sun and nine planets, and three smaller stanchions that provide entry points to the exhibition, and address asteroids and comets.

2000 feet, yet the scale is 1 to 10,000,000,000. Wow. The solar system really is big! And I bet a lot of people have the sore feet to prove it.