lcross moon impact
Image of the impact site for LCROSS.

LCROSS Moon Impact Not Much to Look At: Scientists Hope Spectrometer Data Will Show Water on the Moon

October 09, 2009 07:30 PM
by Haley A. Lovett
Early this morning, the Centaur rocket, followed by the LCROSS craft, collided with the moon in an attempt to stir up a plume of dust that scientists hope will reveal deposits of ice on the moon.

More to LCROSS Success Than Visible Plume, Scientists Say

Although the LCROSS (Lunar Crater Observing and Sensing Satellite) mission is considered a success, observers on the ground were disappointed by the lack of a visible plume of dust after impact.

The LCROSS mission launched on June 18, along with the LRO (Lunar Reconnaissance Orbiter). The LRO will spend a year in low orbit around the moon, mapping the planet and looking for resources that could be useful during future manned missions to the moon, such as water or minerals.

LCROSS brought with it a rocket—Centaur—that was destined to hit the moon in a spot permanently shadowed and extremely cold. Upon impact the LCROSS craft would gather information about any particles it dispersed, and take visual and infrared readings of the impact before hitting the moon itself. NASA researchers were hoping that Centaur’s impact would throw particles higher than the shadowed area of the crater, where sunlight would vaporize them, allowing the LCROSS craft to detect water or any other elements.

When the Centaur rocket hit the moon this morning around 4:30 a.m. PST, the LCROSS craft’s infrared cameras were able to capture the impact. Those observing via telescope, however, did not see the expected miles-high plume.

In the post-impact news conference, LCROSS principal investigator Anthony Colaprete explained that the absence of a large visible plume could mean a number of things: that the impact caused matter to be ejected laterally instead of straight up; that the type of material hit was not loose rock but rather bedrock; that something about the composition of the material itself made the plume difficult to see; or that the shadow heights within the crater were larger than expected.

According to New Scientist, one observatory, Kitt Peak in Arizona, did detect the presence of a sodium flash. This, according to Colaprete, means that something in the debris from the impact or in the atmosphere “excited” sodium molecules; what exactly that was remains to be seen.

For the most part, it seems much more analysis of the data recorded by NASA and by other observers of the impact is needed to conclusively say whether there is water and ice in the dark craters of the moon, and to fully evaluate the experiment. NASA hopes to use the LCROSS mission as a template for future missions because it was executed in a relatively short timeframe, with a comparatively small budget.

Why Look for Water on the Moon?

In September of this year, some of the early information returned from the LRO indicated that the permanently shadowed areas on the moon are extremely cold (-397 degrees), and could contain ice deposits. Water would not last long outside of those very cold areas on the moon. Once exposed to the sun, the water would vaporize and leave the moon’s surface.

Three recent studies found that water is in fact present on the moon in trace amounts. The water particles are mixed with the other elements present on the moon’s lit surface, and the amount of water particles is so small that it would be drier than any desert on Earth.

Scientists are searching for large water ice deposits on the moon’s poles because such deposits would make long-term stay on the moon more practical, by providing astronauts with sources of water and minerals that would otherwise need to be transported. Also, the molecules that comprise water could be used to make fuel, and might be needed for the return trip to Earth.

What Effect Will the LCROSS Impact Have on the Moon?

Some were worried about the potential effect of crashing a spacecraft into the moon. Pete Spotts of The Christian Science Monitor helps explain that the impact with the moon was improperly dubbed a “bombing” of the moon. “Nothing exploded,” he wrote, “although two spacecraft—one about the size of a bus, the other a subcompact car—did crash on the surface of the moon.”

NASA explains that the relatively slow velocity of the crafts hitting the moon would make an impact comparable to that of a 22 lb. meteorite hitting the moon’s surface. Without an atmosphere to help burn up asteroids and other space objects, objects of this size hit the moon a few times a year already. NASA doesn’t expect any of the ejected matter from the impact site to go into orbit around the moon. In addition, researchers believe that the impact crater created when the LCROSS rocket hit the moon was about the size they’d estimated—roughly 20 meters in diameter—and that a crater that size is incredibly common on the moon.

LCROSS Not the First Time NASA Uses Twitter to Connect With Public

During the mission, NASA set up an LCROSS Twitter account, with messages from the LCROSS craft sent to its followers until it hit the moon. The final in-flight message was, “That’s it! Ground! Ha! I wonder if it’ll be friends with me?” and then messages were taken over by the Science Team at Ames.

But LCROSS isn’t the first NASA endeavor to use Twitter to connect directly with the public. In an attempt to foster a better public image, NASA has been using the mircoblogging service to send messages about, and even from, space. Astronaut Mike Massimino used the service to send updates to his followers about the Hubble repair mission last spring.

When concerns arose last May that the GPS system could potentially crash, NASA again used Twitter to answer questions from the public and the press, ushering in a new era of direct communication between a government agency and the public.

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