Large amounts of water have been found trapped in volcanic deposits across the surface of the moon, which means the lunar mantle is probably a far wetter place than anyone ever thought possible. The finding could call into question our theories about the moon’s formation, but it could also make future moon colonies more feasible, reports Phys.org.
The leading theory for how the moon formed is that it represents debris left behind after a catastrophic collusion between the young Earth and a Mars-sized planet very early in the solar system history. A collision like this should have burned off most of the moon’s hydrogen, an essential ingredient for making water, so scientists have long assumed that the moon was a dry place.
Clues to the moon’s hidden water were first revealed back in 2008, when a research team detected trace amounts of water in some of the volcanic glass beads brought back to Earth from the Apollo 15 and 17 missions. Then, in 2011, the water in those glass beads was further analyzed, revealing that the samples contain similar amounts of water as some basalts on Earth.
Could the moon’s interior therefore contain similar amounts of water as found on Earth’s?
What we know from Apollo
“The key question is whether those Apollo samples represent the bulk conditions of the lunar interior or instead represent unusual or perhaps anomalous water-rich regions within an otherwise ‘dry’ mantle,” explained Ralph Milliken, lead author of the new research. “By looking at the orbital data, we can examine the large pyroclastic deposits on the moon that were never sampled by the Apollo or Luna missions. The fact that nearly all of them exhibit signatures of water suggests that the Apollo samples are not anomalous, so it may be that the bulk interior of the moon is wet.”
To reach their conclusions, Milliken and co-author Shuai Li used a new thermal correction method to analyze the temperature profile of the areas of interest on the moon’s surface. The source data came from the moon Mineralogy Mapper, an imaging spectrometer that flew aboard India’s Chandrayaan-1 lunar orbiter. Temperature profiles can reveal which minerals and other compounds are present on the surface of the moon because wavelengths of light are absorbed or reflected by the surface differently depending on what it’s made up of.
Water was found in nearly all of the large pyroclastic deposits that were mapped. Because these regions were distributed across the lunar surface, it means the detection of water in the Apollo samples was no anomaly. It also indicates the high likelihood that a similar distribution can be found in the moon’s mantle.
If there is (or was) more water, how did it get there?
“The growing evidence for water inside the moon suggest that water did somehow survive, or that it was brought in shortly after the impact by asteroids or comets before the moon had completely solidified,” said Li. “The exact origin of water in the lunar interior is still a big question.”
It might mean that we need to re-formulate our theories about how the moon formed, or at least re-consider how hydrogen might survive under such extreme conditions. There’s also potentially more than enough water to make mining operations on the moon worthwhile. Future moon inhabitants might get enough water from the moon to survive on their own without supplies from Earth.
“Anything that helps save future lunar explorers from having to bring lots of water from home is a big step forward, and our results suggest a new alternative,” said Li.
credit: Bryan Nelson
The age of the moon is the subject of some debate within the scientific community. Some scientists think that the moon formed roughly 100 million years after our solar system formed, while others favor a date somewhere between 150 and 200 million years after the solar system’s birth. These dates would put the moon between 4.47 billion and 4.35 billion years old.
A new study published in Science Advances claims to put the controversy over the moon’s age to rest. A team of researchers think they have accurately dated the moon at 4.51 billion years old.
The researchers used moon rocks taken from the lunar surface during the Apollo 14 mission in 1971 for their study. Most moon rocks astronauts have brought back to Earth are composites of rocks fused together during meteor strikes, and that makes dating them tricky as the different pieces of the rocks will reflect different ages. To get around this, the researchers turned to zicorn, a very durable mineral found in both the Earth’s crust and in moon rocks.
“Zircons are nature’s best clocks,”said co-author Kevin McKeegan, a UCLA professor of geochemistry and cosmochemistry. “They are the best mineral in preserving geological history and revealing where they originated.”
McKeegan and lead author Mélanie Barboni focused on the tiny zicorn crystals that contained small amounts of radioactive elements, particularly uranium and lutetium. They isolated when these two elements has decayed to calculate how long the zicorn had formed and used that to provide what they contend is an accurate age for the moon.
This isn’t to say that the zicorn-dating approaching is without its own controversy. Speaking to The Verge about the findings, Richard Carlson, the director for the department of terrestrial magnetism at Carnegie Institution for Science, he praised the work but cited concerns about the zicorn approach. Namely, Carlson questions the assumption that the decayed ratios for the uranium and lutetium would be the same in the early days of the solar system as they would be today.
“It’s just a very complicated problem they are addressing here, which is why we still don’t have a clear answer to such an obvious question as the age of the Moon,” Carlson said.
Source: mnn.com Continue reading “How old is the moon?”