With the regular expeditions of various space agencies to the Moon, our celestial neighbour was thought to be well understood by scientists. A new discovery, however, has brought an end to that notion and is now baffling scientists like never before - the discovery of rust.
As per a new study that has now been published in the journal Science Advances, scientists have found haematite on the Moon. An oxidised form of iron, formation of haematite on Earth requires both air and water.
Since the Moon has no known sources of both, the discovery has been puzzling the scientists since coming to light. There is practically no air on the Moon, while the presence of water is mostly in the form of ice.
Another reason that should have possibly prevented the formation of haematite on the Moon is the constant solar wind that it faces. The stream of hydrogen constantly bombarding the Earth and its natural satellite acts as a reducing agent. Moon does not have a magnetic field as Earth to shield it from this hydrogen stream.
This means that the hydrogen stream donates its electrons to the interacting materials. Since oxidisation that results in rust formation occurs due to a loss of electrons, the solar wind should have cancelled out the haematite formation.
Shuai Li, the lead author on the study, and his team were able to make the discovery using data from Indian Space Research Organization's Chandrayaan-1 orbiter. The orbiter discovered water ice on the Moon and mapped out a variety of minerals while surveying the lunar surface in 2008.
Shuai Li, of the University of Hawaii, studied that water extensively.? The data was recorded from Chandrayaan-1's Moon Mineralogy Mapper instrument (M3), built by NASA's Jet Propulsion Laboratory (JPL).
M3 was able to detect the light reflected off the Moon¡¯s polar rocks. The findings revealed that the Moon's poles ¡°had a very different composition than the rest of it.¡± Upon closer inspection Li, discovered the rocks to have traces of hematite or rust.
"It's very puzzling," said Li in a release by NASA, adding "the Moon is a terrible environment for haematite to form in."?
Shuai Li, along with JPL scientists Abigail Fraeman and Vivian Sun, studied the findings extensively to come up with three possible explanations for the mystery in their research.
The first one explains the presence of Oxygen. The paper highlights that even without an atmosphere, there are traces of oxygen on the Moon. Interestingly, the source of that oxygen is Earth.
The 385,00 kilometers travel of the Oxygen is explained by a 2007 discovery by Japan's Kaguya orbiter. The orbiter discovered that oxygen from Earth's upper atmosphere can ¡°hitch a ride¡± on the Earth¡¯s trailing magnetic field that acts just like a shadow, thus reaching the Moon.?
The model fits with the recent finding, as more hematite was found on the Moon's side facing the Earth rather than on its far side. "This suggested that Earth's oxygen could be driving the formation of hematite," Li said.
For the water molecules needed for the rust, the paper explains the presence of these in the lunar surface. As per Li, fast-moving dust particles that constantly bombard the Moon could release these surface-borne water molecules.
Third explanation targets the hydrogen stream as the deterrent for rusting. The paper explains that the Earth blocks over 99% of the solar wind during certain periods of the Moon's orbit. Specifically, this takes place during the full Moon phase. These thus open ¡°occasional windows during the lunar cycle¡± when rust can take place.
The NASA release clears that still more data is needed to completely understand this interaction of water with lunar rocks. This data could possibly also explain the presence of hematite on the far side of the Moon.