LCROSS Update: Mercury and Iron Possibly Found in Impact Plume


Kelly Beatty has an update on the LCROSS findings over at Sky & Telescope. NASA scientists are still analyzing data and may announce some preliminary results (including the discovery of water) at the Lunar Exploration Analysis Group meeting in Houston on Nov. 16-19.

For now, let me tantalize you with a preliminary result from the Lunar Reconnaissance Orbiter, which viewed the Centaur’s demise from nearly overhead and just 48 miles (76 km) up. An instrument dubbed the Lyman-Alpha Mapping Project (LAMP) probed the ultraviolet spectrum of the impact plume after it had risen high enough to be projected against black space above the lunar limb.

“We definitely saw something,” notes LAMP scientist Randy Gladstone (Southwest Research Institute). But that “something” wasn’t water. Nor was it oxygen or hydrogen atoms, both of which have strong ultraviolet emissions. There’s some hint of hydrogen molecules (H2) — and though water is one source of hydrogen, it could also have come from silicate minerals, solar-wind gas trapped in the lunar soil, or (most likely) residual fuel in the Centaur’s tanks.

LAMP’s strongest and most intriguing observation came at the ultraviolet wavelength of 184-185 nanometers. Gladstone says the only known elements able to create that line are iron, perhaps magnesium … and mercury. “Both mercury and iron still look like the best bets for explaining the plume emission we see with LAMP,” Gladstone reiterates, though the spectral match is still tentative and more data-crunching is in progress.

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