In a discovery that may solve the mystery behind the source of moon’s water, an evidence from NASA’s LCROSS mission suggested that much of it was delivered by comets that slammed into the Earth’s satellite billions of years ago.
Previous missions had also found hints of lunar water but its source was never clear. One idea is that it forms when hydrogen atoms from the solar wind latch onto oxygen atoms in the lunar soil, creating hydroxyl and water.
According to the data revealed recently at the Lunar Exploration Analysis Group meeting, a gathering of 160 lunar scientists in Houston, the evidence is mounting in favour of an alternative explanation — comet impacts.
The first line of evidence comes from compounds that vaporise readily, called volatiles. LCROSS found spectral signs of volatiles containing carbon and hydrogen — likely methane and ethanol — as well as others such as ammonia and carbon dioxide, journal New Scientist reported.
“It appears that we impacted into a very volatile—rich area,” LCROSS principal scientist Tony Colaprete said.
These compounds should have been mostly lost to space billions of years ago, when the moon coalesced from the debris of an impact between the Earth and a Mars—sized object.
Water formed through an interaction with the solar wind would therefore be relatively pure — and free of volatiles.
But comets, which are thought to have been responsible for many of the moon’s impact scars, are “dirty iceballs” known to contain volatiles such as methane.