A new study from the Moscow Institute of Physics and Technology suggests that water reserves detected on the moon were caused by asteroids supplying the water as “delivery vehicles,” as opposed to what was originally theorized.
Earlier theories had stated that falling comets were the source of the moon’s water reserves. But MIPT and RAS Geosphere Dynamics Institute scientists found out that a large asteroid is capable of delivering more water to the moon’s surface than all of the comets that had fallen to the moon over the past one billion years. Findings of their study were elaborated on in the journal Planetary and Space Science.
Back in the 1960s, during the Apollo program’s heyday, NASA scientists had thought that the moon was completely dry. The early satellites of that era had gathered data suggesting that the lack of atmosphere and the impact of solar radiation combined to make the lunar surface dry, as both were thought to be capable of evaporating any volatile substance. But in the 1990s, the Lunar Prospector probe had refuted that theory. The neutron current discovered from the moon’s surface suggested that there was more hydrogen than once thought at the near-surface soil in some parts of the moon. This brought up the possibility that there may be lunar water reserves after all.
This urged scientists to come up with the “cold traps” theory, which sought to explain how the moon’s surface could hold in some water reserves. As the moon’s rotational axis is almost vertical, the polar regions of the satellite have craters with floors that never get to see any sunlight. And when comets made primarily of ice water fall, evaporated water falls into those traps and stays there for an indefinite period of time, due to the lack of sunlight penetrating through. That was the popular theory held for several years, until the new MIPT study that tells us the source of that water may not come from comets after all.
A number of missions from the 21 stcentury have helped today’s scientists come up with some new and revealing information. The LCROSS experiment, for one, has proven that the moon has significant amounts of water and hydroxyl groups in its near-surface soil. But another new revelation, this time from Russia’s LEND instrument on board the American Lunar Reconnaissance Orbiter, debunked the seemingly proven theory that that water had come from comets.
According to the data gleaned from the LRO, the cold trap map didn’t match its map of water distribution. Scientists had to fine-tune the theory, and had eventually discovered that not all the water that comes when a comet falls stays for an extended period of time. “We came to the conclusion that only a very small amount of water that arrives with a comet stays on the moon, and from this decided to explore the possibility of an asteroid origin of lunar water,” said researcher Valery Shuvalov in a statement.
After studying asteroids, Shuvalov and his colleagues discovered that they are made up of non-differentiated construction materials of the solar system, and do contain a lot of water in them. The researchers singled out chondrite carbonaceous as having a 10 percent water makeup. Water in chondrite asteroids is protected well by crystallized minerals, and only seeps out when heated to 300-1,200 degrees Celsius.
“We’ve concluded that the fall of asteroids containing water could generate ‘deposits’ of chemically bounded water inside some lunar craters,” Shuvalov added. “The fall of one two-kilometer size asteroid with a rather high proportion of hydrated minerals could bring to the moon more water than all of the comets that have fallen over billions of years.”