The Stratospheric Observatory for Infrared Astronomy (SOFIA) has detected evidence of molecular water in the regolith of Clavius Crater, a large crater visible from Earth in the Moon’s southern hemisphere. The airborne SOFIA observatory, a partnership between NASA and the German Aerospace Center, flies in a modified Boeing 747SP aircraft above the atmospheric water that blocks ground observation.
Satellites have had detected “hydrates” in the lunar regolith but could not distinguish between OH (hydroxyl) and H20 (molecular water). SOFIA was able to measure the precise being vibration of the H-O-H molecular bond at 6.1 µm in the infrared.
SOFIA targeted high lunar latitudes near the South Pole where low temperatures could allow migrating water to transiently remain on the surface and high hydroxyl abundances could create and trap water when impacted by small meteorites. Although Clavius has a relatively high concentration of water by lunar standards, says NASA, it is roughly one-hundredth of the water found in the Sahara desert. more “Molecular Water Found in Clavius Crater”
According to the latest estimates by a team of researchers with the Technische Universität Berlin, it might have taken ten times longer than previously thought for the early Moon to transform from a ball of super-heated magma into its current form.
The oldest rock found on the Moon, brought to Earth by the Apollo 14 mission, has been dated to 4.51 billion years old, comparing to the estimated 4.54 billion years estimated for the age of the Earth. But minerals can go back only as far as the moment when those minerals formed. To date the Moon, scientists need to know how much time elapsed until the magma ocean solidified, explains Sky & Telescope.
Maxime Maurice and his colleagues at the German university have developed a new thermal evolution model — a detailed computer simulation — to reconstruct the first 200 million years of lunar evolution. Their studies identified two previously underappreciated dynamics: the insulating effect of the primordial lunar crust, and mantle convection that probably started even before the magma ocean completely solidified.
It has been long known that the early Moon formed a crust made of a light mineral called pagioclase, which floated atop the magma ocean. That crust turned out to be an excellent insulator. While previous studies had accounted for that effect, Maxime concluded the insulating effect had been under-estimated.
The other factor was mantle convection. Summarizes Sky & Telescope:
The lunar magma ocean solidified from the bottom up because high pressure at depth forced the magma to solidify even at high temperatures. This process likely solidified 80% of the magma ocean within 1,000 years of the Moon’s formation. If mantle convection started at this point, it could have allowed heat to continue flowing from the depths toward the surface, keeping the magma ocean hot and molten.
On Earth, mantle convection creates the magma that feeds volcanoes. “In this case, it would be exactly the same, but the volcanoes would have spilled their lava into the magma ocean,” Maurice explains.
Until now, van Westrenen says, most lunar evolution scenarios assumed that mantle rocks didn’t start moving until the magma ocean had completely solidified.
According to van Westrenen, the combination of these two processes makes a huge difference for the longer-term survival of the magma ocean.
A slowly crystallizing magma ocean could require a reinterpretation of mineral isotope dating of many lunar samples, and thus for the aging of the Moon-forming impact. The bottom line, the Moon may be 100 million years younger than commonly postulated.
It has been an enduring mystery why the side of the Moon facing the Earth is marked by large dark patches, called maria (or seas, as they once were thought to be) but the far side has very little. Thirty-one percent of the near side consists of maria, but the dark side has only one percent. The maria, which are vast plains of basalt, most likely were formed by volcanic activity early in the Moon’s history.
But why the disparity between the near side and the far side? Scientists think that a clue resides in the distinctive characteristics of the rock. Based on samples that Apollo astronauts brought home from the maria, scientists found that the rock had a unique signature, which they named KREEP — for the presence of potassium (chemical symbol K), rare-earth elements (which include cerium, dysprosium, erbium, europium and others), and phosphorous (chemical symbol P) — as well as uranium and thorium.
By melting KREEP rock in high-temperature experiments, scientists from Tokyo’s Earth‐Life Science Institute (ELSI), the University of Florida, the Carnegie Institution for Science, Towson University, NASA Johnson Space Center and the University of New Mexico think that radioactive decay of some of these elements released heat that could have influenced the timing and volume of volcanic activity.
According to Phys.Org, potassium, thorium and uranium are radioactively unstable elements. appearing in a wide variety of isotopes. When the atoms break down, they yield other elements and produce heat. The heat from this radioactive decay can melt the rocks they are contained in.
Says EKSI’s Matthieu Laneuville: “Because of the relative lack of erosion processes, the moon’s surface records geological events from the solar system’s early history. In particular, regions on the moon’s near side have concentrations of radioactive elements like U and Th unlike anywhere else on the moon. Understanding the origin of these local U and Th enrichments can help explain the early stages of the moon’s formation and, as a consequence, conditions on the early Earth.”
The formation of ancient rocks on the Moon may be directly linked to large-scale meteorite impacts, concludes a group of international scientists led by the Royal Ontario Museum after research a unique rock collected by NASA astronauts during the 1972 Apollo 17 mission to the Moon. The rock contains mineralogical evidence that it formed at incredibly high temperatures, in excess of 2300 °C/ 4300 °F, that could have been achieved by the melting of the outer layer of a planet in a large-impact event, reports Science Daily.
Researchers discovered in the rock the presence of a mineral known as baddeleyite, a stable phase arising from cubic zirconia, commonly used on earth as a substitute for diamonds in jewelry, which could have been formed only in rocks heated to above 2300 °C. While examining the structure of the crystal, the researchers measured the age of the grain, which reveals the baddeleyite formed over 4.3 billion years ago. Given that the high-temperature cubic zirconia phase must have formed before this then, they concluded that large impacts were critically important to forming new rocks on the early Moon.
“Rocks on Earth are constantly being recycled, but the Moon doesn’t exhibit plate tectonics or volcanism, allowing older rocks to be preserved,” explains Dr. Lee White, Hatch Postdoctoral Fellow at the Museum. “By studying the Moon, we can better understand the earliest history of our planet. If large, super-heated impacts were creating rocks on the Moon, the same process was probably happening here on Earth.”
Adds Dr. James Darling, a reader at the University of Portsmouth and co-author of the study. “These unimaginably violent meteorite impacts helped to build the lunar crust, not only destroy it.”
Once upon a time the Moon had a magnetic field, and it was likely stronger than Earth’s is today. That field, generated by a powerful dynamo in the Moon’s core, petered out about one billion years ago.
The latest theory, propagated by MIT scientists in the journal Science Advances, suggests that crystallization of the Moon’s inner iron core stirred the electrically charged fluid and produced the dynamo.
“The magnetic field is this nebulous thing that pervades space, like an invisible force field,” says Benjamin Weiss, professor of earth, atmospheric, and planetary sciences at MIT. “We’ve shown that the dynamo that produced the moon’s magnetic field died somewhere between 1.5 and 1 billion years ago, and seems to have been powered in an Earth-like way.”
Most studies of lunar magnetism have been based on rock samples from the Apollo missions; most of the ancient rocks are estimated to be thee to four billion years old. When they were spewed out as lava, their microscopic grains aligned in the direction of the Moon’s magnetic field. Lunar rocks whose magnetic histories began less than three billion years ago do not show such alignment, which suggests that lunar vulcanism had largely ceased by that time.
The MIT scientists theorize that the early Moon was much closer to the Earth than it is today, and much more susceptible to its gravitational effects. In a phenomenon known as “precession,” the solid outer shell of the cooling Moon wobbled in response to the Earth’s gravity. The wobbling stirred up the fluid in the core, the way swishing a cup of coffee stirs up the liquid inside, explains MIT News.
As the moon moved slowly away from the Earth, the precession effect decreased, weakening the dynamo and the magnetic field. About 2.5 billion years ago, core crystallization became the dominant mechanism by which the lunar dynamo continued, producing a weaker magnetic field that continued to dissipate as the moon’s core eventually fully crystallized.
The early Moon likely contained significant volumes of water mixed into its global ocean of molten rock, theorize scientists from VU Amsterdam.
According to the conventional view, the Moon was formed by a collision of a small planetary-sized body with the young Earth that created a swirling mass of debris from which the Earth and the Moon condensed. In a process parallel to Earth’s, the Moon started as a mass of molten rock that slowly cooled over the ages. As it cooled, different minerals solidified at different temperatures and depths.
The Dutch scientists began asking how various mineral mixes behaved under extreme temperatures and pressures. Their models indicate that the Moon must have started with water mixed with the magma. ExplainsArs Technica:
“How do you model an entire ocean of molten rock? You start with the known composition of the Moon and use that to create a mix of the appropriate minerals. Then you expose those minerals to extreme pressures and temperatures well beyond the melting point of rock. For these experiments, the temperatures ranged up to 1,550 degrees Celsius. Since the magma ocean was potentially hundreds of kilometers deep (current estimates range from 400 to 1,000 kilometers), pressures ranged up to 3 GigaPascals, which is nearly 30,000 atmospheres.” more “Early Moon Had More Water than We Thought”
After the solar system formed 4.6 billion year ago, an object slammed into the Moon and formed a 620-mile-wide indentation now known as the Crisium basin. Scientists examining the region say they’ve spotted a crater within the basin that appears to contain pristine impact melt of volcanic rock, reports National Geographic.
Not only might the geologic feature yield clues about the frenzied meteor bombardment during the early history of the Earth and Moon, the basin holds a geologic blister the size of Washington, D.C., unlike any other feature seen in the the solar system. The volcanic lump appears to have been cracked open by underground magmatic activity.
Rocks recovered by U.S. Apollo missions and Russian robotic missions are estimated to be between 3.8 and 4.0 billion years old, leading scientists to theorize that there was spike in the number of impacts on the Moon during a period known as the Late Heavy Bombardment. But that conventional wisdom has come into question. Why was there a 700-million-year quiet period before then?
The Crisium basin could shed light on that mystery. The original impact that formed the basin was so powerful that it created a melt sheet up to 9.3 miles thick. Later, profuse eruptions of lava flooded the basin beginning about 3.6 billion years ago, forming a volcanic sea known as Mare Crisium that covered up much of the original melt. But “islands” of rock within the basin, known as Kipukas, survived the lava inundation. As lunar scientists examined the region, one Kipuka stuck out. Close examination showed that much of it was made of frozen volcanic rock. The research team conjectures that the lump was pushed upward by subsurface volcanic activity, but the origin remains a mystery. more “Geologic Mystery: How Old Is Mare Crisium?”
NASA engineers have proposed sending autonomous drones to the Moon to explore the potential of using lava tubes and caves for human habitation. It is theorized that ancient lava flows from volcanoes left miles of lava tubes up to 30 feet across, reports the Daily Mail.
Meanwhile, researchers at the Morgridge Institute for Research in Madison, Wisc., are developing camera technology to explore the tubes from an orbiting satellite.
States project leader Andreas Velten:
Geologists are interested because they would provide access to subsurface geology without actually having to dig, which would be very difficult. What’s interesting for space travel is you can’t have people on the surface for long periods because of the temperature extremes, and because of radiation. But in these caves, people could survive for a long time with consistent temperatures and no radiation. Some of these may actually be quite deep, under 50-60 metres of rock.
Earlier these year, says the Daily Mail, NASA announced its Periscope Project, with the goal of mapping the tubes by peering into the 200 or so “skylights” that have been discovered so far.
Silver hydroxide molecules released from silicon dioxide in the lunar regolith react easily with hydrogen, leading to the formation of water and silver, scientists with the Higher School of Economics and the Space Research Institute of the Russian Academy of Sciences have found.
The implication is that water and silver molecules can be formed on the Moon. In some areas, the proportion of water formed by this mechanism could exceed 6 to 10%.
“The study demonstrates that water may form due to internal, continuously functioning mechanisms. (Comets hitting the lunar surface is a rather rare phenomenon.) It turns out that the water on the Moon can be present not only in cold traps but also in the near-surface lunar soil,” explained Sergey Popel, a study author and head of the laboratory at the Space Research Institute.
Also, said Popel, the presence of water can affect the phototelectric properties of the lunar regolith and the parameters of the plasma-dust system over the Moon.
The Moon’s thin atmosphere contains neon, NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft has confirmed.
“The presence of neon in the exosphere of the moon has been a subject of speculation since the Apollo missions, but no credible detections were made,” said Mehdi Benna of NASA’s Goddard Space Flight Center in Greenbelt, Maryland and the University of Maryland, Baltimore County in a NASA press release. “We were very pleased to not only finally confirm its presence, but to show that it is relatively abundant.”
Because the Moon’s atmosphere is so tenuous, about 100 trillion times less dense than Earth’s atmosphere are sea level, the volume of neon is minute.
Most of the gases in the exosphere — primarily neon, argon, and helium — comes from the solar win, a stream of electrically conducting gas blown from the surface of the sun into space at about one million miles per hour. All of these elements impact the Moon, but only helium, neon and argon are volatile enough to return to space. A portion of the helium, argon, and neon in the lunar exosphere comes from naturally occurring radioactive potassium-40, thorium, and uranium found naturally in lunar rocks. more “Neon Found in Lunar Atmosphere”