UT researchers have recently uncovered the probable source of water deposits left on the lunar surface.
Lawrence Taylor, professor in the Department of Earth and Planetary Science, has already achieved great acclaim in the scientific community, proving the existence of abundant water deposits on the Moon. His new findings indicate that some of this water originated from various comets’ collision with the moon.
“Cometary water-ice exists in the permanently shadowed craters at the poles of the Moon, where the temperatures are on the order of -230 degrees Celsius — 40 Kelvin,” Taylor said.
His findings have indicated that water deposits may be present inside the moon as well. However, the deposits on the lunar surface could be of significant benefit for space exploration.
“This water-ice will be a challenge for the astronauts to recover, but is in great supply and could provide liquid hydrogen and liquid oxygen as fuel for rockets — having empty gas tanks after escaping Earth’s gravity,” he said.
While Taylor believes comets may be responsible for water deposits on the moon’s surface, he asserted water is in the moon’s interior as well.
“The second form of water on the Moon is that of the ‘space dew’ originally reported by Pieters et al. (2010), and verified by Sunshine et al. (2010) and Clark (2010),” Taylor said. “This surficial, thin layer of water is probably formed by solar-wind proton (H+) bombardment of the lunar soil, creating OH and HOH bonds on the external surface of soil particles. Today we are addressing water in the moon — in minerals that crystallized from the lunar magmas and lavas.
The water that exists inside the moon may be of particular interest for geologists.
“The water in the moon consists of OH discovered in quantities of up to 7000 parts per million (0.7 wt%) in the mineral apatite, a late-stage crystallized mineral that is very rich in ‘incompatible’ elements, such as water,” Taylor said. “The presence of water in magmas and minerals affects many of their physical properties (e.g., density, thermal capacity), which leads us to reconsider the origin of some of the volcanic rocks on the Moon.”
The particular comets, or “dirty icebergs,” are hypothesized to have collided with the early Earth and moon during their developmental stages. Taylor conjectured that these collisions did little to alter the state of planet Earth, but in fact transferred a great deal of moisture to an otherwise dry lunar surface.
“Now we know that at this very early stage of the formation of the moon, there was substantial cometary water input to both the moon and the Earth,” Taylor said. “But, because the Earth already had lots of volatiles, this new input made little difference to the overall Earth water system. However, the dry moon absorbed this cometary water with its distinct D/H signature. As the moon cooled from a largely molten mass, this water became part of the overall magma and rock systems of the moon.”
Taylor’s findings indicated, however, that the water on the moon originated from internal sources as well as collisions with external forces of solar wind and comets.
Taylor has explored the composition of lunar materials by employing secondary ion mass spectrometry to search for traces of water origins among rock samples brought back from the Apollo space missions. He anticipated further applications for this advancing technology.
“We must search for water that is undoubtedly present in many other lunar minerals, pushing the cutting-edge capabilities of the analytical instrumentation — Secondary Ion Mass Spectrometer (SIMS),” Taylor said.
This water does not exist in the form of water on earth, but instead consists of the elements hydrogen and oxygen, which could become water when liberated from their sources by heat.
With these elements present on the lunar surface, the moon can potentially be used as a refueling station for space missions. Spacecraft could use liquid hydrogen and liquid oxygen as fuel to reach planets that are farther away.
“Science moves ahead as the capabilities of our sophisticated instrumentation become more capable of detecting smaller quantities of chemistry,” Taylor said. “As new instrumentation is developed, new scientific aspects can be addressed with these new capabilities.”
Taylor’s findings were developed with the help of dedicated assistants.
“The paper established the presence of water in the moon,” Yang Liu, research assistant professor in the Department of Earth and Planetary Sciences, said. “Such a landmark finding opens new avenues for understanding the formation of the Earth-moon system, evolution of the moon and may even shed light on the origin of water on Earth.
Nature Geoscience, a leading scientific publication, will post Taylor’s findings online under the title “Extraterrestrial Hydrogen Isotope Composition of Water in Lunar Rocks.”
