Monday, August 3rd, 2009
The second of the two moon missions that NASA launched in June is called LCROSS, an acronym for Lunar Crater Observation and Sensing Satellite. According to Tony Colaprete, the chief scientist for the LCROSS mission, “The younger folks at Goddard Space Flight Center have started calling it LRO’s BFF… at least until October 9.”
Hmmm… I can see some puzzled looks out there. Okay, I’ll explain. LRO is the Lunar Reconnaissance Orbiter (LRO), which launched on the same rocket as LCROSS on June 18. BFF is Internet-speak for “best friends forever.” (But you knew that already, right?) And October 9 is D-day for the LCROSS mission. Unlike LRO, which will accumulate its results slowly and steadily over a period of one to three years, LCROSS will go out in a blaze of glory, and will do all of its most interesting science over the course of 5 minutes.
LCROSS consists of two main pieces — a spent rocket booster and a “shepherding satellite.” On October 9, around 4:30 AM Pacific time, the bigger rocket booster will slam into a crater near the moon’s south pole. Imagine an SUV crashing head-on into the ground at more than 5000 miles per hour! That’s what the impact is going to be like. It will be equivalent to the explosion of about a ton of dynamite.
The explosion will be big enough, in fact, to be seen from Earth. That is the whole idea — to time the impact so that it can be tracked by all of the big telescopes on Hawaii, as well as the Hubble Space Telescope. Colaprete says that even a 10-inch telescope (well within the range of many amateur astronomers) should be able to see the flash, if it is pointed in the right place at the right time. If you don’t have access to a 10-inch telescope, you can also watch the impact over the Internet.
A minute or so after the big kablooie, the shepherding satellite will come swooping in, flying right through the debris plume. While it’s getting buffeted about, it will hopefully be able to sniff out any volatile compounds that have been excavated by the blast, including water vapor — the number one target of the mission.
We’ve seen tantalizing hints of water ice from orbit, but nothing that absolutely confirms it. We know that there is hydrogen in the permanently shadowed craters near the south pole, but there is no guarantee that the hydrogen is bound up with oxygen to make a water molecule. There’s only one way to find out for sure, and that is to “reach out and touch it,” as Colaprete says. Or perhaps “reach out and blow it up” would be a slightly more accurate wording.
After it flies through the plume, the shepherding satellite will itself crash into the moon a few minutes later, creating a second and smaller blast. Colaprete is deliberately not building up any great expectations for this one, because it will be harder to control where the shepherding satellite lands. However, it will give scientists a second chance to look for signs of water, or at least to understand the mechanical properties of the ground that LCROSS is crashing into.
Last month I had a chance to interview Colaprete by e-mail and then in person at the Moon Fest. I also went to his talk at the Lunar Science Forum. In my next post I will try to reproduce these three “conversations” as if they were all one interview.
By the way, the LCROSS mission reminds me of something interesting I learned when researching my moon book. After Russia launched Sputnik in 1957 and when our scientists and politicians were debating what we could do to respond, one of the crazy ideas that was floated was to nuke the moon. That’s right, launch a nuclear missile at the moon and blow it up, thereby proving somehow that we were bigger and badder than the Russkies.
What a stupendously bad idea this would have been, because we would have learned nothing from it. The response we chose instead — sending men to the moon — was vastly more difficult, but we got so much more out of it, including a real understanding of the moon’s origin and makeup, plus the fleeting goodwill of all of the rest of the world.
It’s just a tiny bit ironic, then, that on our second round of missions to the moon, one of the first things that we are doing is slamming a rocket as hard as we can into the moon to create a big explosion. I mention this parallel with some hesitation, because I don’t want to make LCROSS seem like just a stunt. That is exactly what it is NOT. There are two huge differences between this mission and the stunt that was proposed back in the late ’50s:
- A spent rocket booster is not a nuke.
- The LCROSS mission was designed with a specific scientific purpose in mind: to excavate water ice, to see first of all if there is any ice there and secondly how much there is and how easy it is to get it out. These are vital things to know if we are ever going to set up a permanent moon base.
Maybe these points are obvious and didn’t even need saying, but I just wanted to explain why the LCROSS mission is not just about some engineers blowing things up for fun.
(Still, blowing things up is fun … See any episode of Mythbusters for proof!)