[Update (20:30 UT): The mission launched on time, and everything looks good so far! As I write this, the probe's orbiting the Earth. In a few hours (a little after 01:00 UT) it will make its burn to send it on its way to the Red Planet. Congrats to everyone involved in this mission!]
[UPDATE 2 (05:00 UT): There are problems, potentially serious ones, with the mission. As I write this what happened is not clear, but Emily is keeping up with the news.]
[UPDATE 3 (Nov 9, 16:00 UT): It looks like the spacecraft is in safe mode, meaning it shut itself off to prevent damage due to an unforeseen problem. The burn to move it out of Earth orbit and no to Mars did not occur, which means it still has all its fuel. This is very bad, but perhaps not catastrophic. Emily has the details.]
The Russian Mars probe Phobos-Grunt -- which will land on the Martian moon Phobos and return a sample to Earth! -- is scheduled to launch today at 20:16 UT (15:16 Eastern US time). As usual with planetary missions, Emily Lakdawalla has the details. The launch will be streamed live on SpaceflightNow.
Grunt means "soil" in Russian; the name is a little misleading since soil technically is rock and other material broken down in part by bacterial processes. A better term is regolith, but I'm just being pedantic. The important thing to note is that if all goes well this probe will return a sample of the surface of another planet's moon back to Earth!
We still don't understand Phobos all that well; it may be a captured asteroid orbiting Mars, and its surface is weird, as you can see in the picture above. It's lined with grooves, which may have formed when asteroid impacts on Mars below blasted up material, which the tiny rock then plowed through. That's still being argued about. A sample return might help resolve issues like that (for example, finding clear evidence of Martian minerals in Phobos samples). I'm not a geologist, or an asteroid expert, so I'm just excited that a) this probe is going to get intense images of Phobos, 2) we're going to expand the boundaries of science once again, and γ) there will be even more new mysteries to solve once the material is studied, too.
And it all starts today, in a few hours.
Credits: ESA/DLR/FU Berlin (G. Neukum)