Geophysical Research Letters reports that scientists have confirmed the presence of oxygen in the upper atmosphere of Dione, one of Saturn’s many moons.  The international team responsible for the announcement reported that it noticed the trace amounts of the element from data collected by NASA’s Cassini spacecraft.

A sensor on the Cassini spacecraft, named the Cassini Plasma Spectrometer, picked up signals that indicated oxygen ions were present in an area of space where Dione had just been during a pass by the moon in 2010.  After another recent run, the team was able to verify that oxygen does in fact exist in Saturn’s moon, although not in large amounts.

According to Team Leader Robert Toker: “It’s not enough to sustain life, but–together with similar observations of other moons around Saturn and Jupiter–these are definitive examples of a process by which a lot of oxygen can be produced in icy celestial bodies that are bombarded by charged particles or photons from the Sun or whatever light source happens to be nearby.”

The amount of oxygen present in Dione is roughly the equivalent of what is present in the Earth’s atmosphere at an altitude of 300 miles. Dione was discovered in 1684 by the astronomer Giovanni Cassini, who lends his name to the aforementioned spacecraft.  Dione is one of 62 known moons that orbit Saturn.  It is small, clocking in at only 700 miles wide.  Its surface exists only as a thick layer of watery ice that bears marks and scars from an innumerable number of asteroid collisions, inside of which lies a hard, solid core.

Although Dione and the Earth’s moon both orbit their respective planet at around the same distance, Dione completes its orbit in roughly a tenth of the amount of time Earth’s moon does, coming full circle in about 2.7 days.

As it circles Saturn, Dione is assailed by ions, or charged particles, from Saturn’s magnetosphere.  These hit Dione’s icy surface with enough strength to violently throw up molecular oxygen ions into the moon’s small atmosphere, in a process that is known as sputtering.  The oxygen particles are then pulled away from Dione by Saturn’s magnetosphere.

Although the announcement has disproven the idea of life existing on Dione, showing its oxygen levels are much too low, it has opened the door for different possibilities.  Other icy worlds and moons not thought to have oxygen could now be shown to harbor the element within their atmospheres, and with such discoveries comes the tantalizing idea of oxygen-based life forms.  Hopefully more research can shed light on the subject.

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Earlier this week, a group of scientists working at the VU Amsterdam University in the Netherlands conducted an experiment in which they learned how the Moon’s interior is truly structured: below the thin rocky surface (otherwise known as a lithosphere) churns a thick mantle of liquid magma.

The team was led by Mirjam van Parker and Wim van Westrenen and consisted of scientists from the Universities of Paris 6/CNRS, Lyon 1/CNRS, Edinburgh, and the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Using copies of 380 kilograms worth of lunar rock samples that were collected by the astronauts from the Apollo missions, the scientists melted them with a high electric current at a temperature of 1,500˚F, then compressed them at a pressure of 4,500 bar. The aforementioned temperature and pressure are thought to be at the same intensity as the ones underneath the Moon’s surface.

After this, the team measured the samples’ density with powerful x-ray beams emitted from a synchrotron, provided by the ESRF. They learned that the molten rock (the magma) was quite dense – much denser than they had assumed – and that it was liquid, filled with titanium.

These results have disproven a commonly referenced hypothesized cross-section that scientists constructed in the past: first is the thin crust, which is not uniform in thickness around the surface; below is a thick, solid mantle; following is a thinner mantle known as the moonquake zone, which is slightly less solid than the upper mantle, so that seismic waves can travel; and, finally, a solid iron-rich core lies in the center.

The Moon lacks current volcanic activity because the magma is too dense, or just a bit too firm; lighter liquid tends to be pushed up more, similar to the magma under the Earth, and there must be a difference in density between the magma and the surrounding solid material for any eruptions.

“Today, the Moon is still cooling down, as are the melts in its interior,” Wim van Westrenen, the chair of the Netherlands Platform for Planetary Science, states in the ESRF’s news release. “In the distant future, the cooler and therefore solidifying melt will change in composition, likely making it less dense than its surroundings.

This lighter magma could make its way again up to the surface forming an active volcano on the Moon – what a sight that would be! – but for the time being, this is just a hypothesis to stimulate more experiments.” He and Mirjam van Parker have published the findings of their experiment in the journal, ‘Nature Geosciences’, on February 19.

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In September 2011, for the 11th mission of their Discovery Program, NASA launched the twin spacecraft GRAIL (Gravity Recovery And Interior Laboratory), GRAIL A and GRAIL B, which entered the Moon’s orbit during New Year’s weekend. For the first six months of 2012, the spacecraft will produce the most detailed and accurate map of the Moon’s gravitational field yet.

The Moon, the earth’s natural satellite, has the most unique gravitational field of all the other rocky bodies’ in the inner solar system: it is lumpy, and the lumpiest of them all. The surface, which generally affects gravitational fields, is itself lumpy, having various geological structures, such as craters, smooth plains, flat lava flows, and mountains. The surface came to be as it is today because asteroids and other space junk smashed into the natural satellite when it was still forming.

To measure its gravitational field, GRAIL A and GRAIL B will orbit the Moon at a low altitude. This way, their instruments would be more sensitive and will more likely produce accurate results. Orbiting in tandem, they will measure the changes of the distance between each other caused by the differences in strength of the field.

NASA plans for the mission to end in June, but hopes to keep the twin spacecraft studying the Moon for an additional six months to find out additional information about the natural satellite. Through mapping the gravitational field, GRAIL A and GRAIL B can also study the structure of the lithosphere (the crust) and what the Moon is like below the surface. They may then find out if there is presence of a solid core and discover what the Moon’s thermal evolution was like (i.e. how the natural satellite heated and cooled).

If GRAIL A and GRAIL B successfully determined all of this information, we would be given insight as to how the Moon formed.

“This mission will rewrite the textbooks on the evolution of the Moon,” says Maria Zuber in a NASA press release. Zuber is the GRAIL principal investigator from the Massachusetts Institute of Technology.

In turn, we would discover the planetary evolution process of other rocky bodies in the solar system, particularly Earth’s, since the Moon is essentially an entire geological record of the solar system, which is aged 4.5 billion years.

Charles Bolden, NASA Administrator, adds in another NASA press release, “NASA greets the new year with a new mission of exploration. The twin GRAIL spacecraft will vastly expand our knowledge of our moon and the evolution of our own planet. We begin this year reminding people around the world that NASA does big, bold things in order to reach for new heights and reveal the unknown.”

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A recent study published in Nature has shown that the moon may not be as old as once thought. With samples brought back from the Apollo 16 mission, researchers at California’s Lawrence Livermore National Laboratory have determined one of two things: that either the moon is about 60 million years younger than thought, or the molten stage of development solidified later than previous estimates.

In the prevailing theory, during formation, as the magma of the moon cooled, crustal moon rocks formed called ferroan anorthocites. These mineral rocks have proved difficult for scientists, when it comes to scientifically dating them.

Lars Borg, from the Lawrence Livermore National Laboratory said that with these samples, he and his colleagues have seen the first success in yielding consistent ages using multiple dating techniques. Borg and his colleagues utililzed new refining techniques to reach the new consistent age.

“Previous attempts to date these rocks have relied on just one isotopic clock which can be contaminated putting the age in error,” said Borg in a Discovery News article. “So we started with the idea that we would get multiple age samples so we could have confidence it reflected the crystallization age of the sample.”

The new projected age of the moon falls right around the age of the oldest crusts on Earth at about 4.36 billion years old. This number represents what scientists have found to be when the rock crystallized.

These new findings do oppose the popular “giant impact theory” of the moon’s formation. However, this research is not providing a clear alternative to this theory. Clive Neal, a planetary geologist at the University of Notre Dame told the Los Angeles Times that the researchers need more evidence. Before coming to the conclusion that the theory has been disproved, there must be more evidence of inaccurately dated rock samples.

Apollo 16 launched in 1972, as the tenth manned mission in the American Apollo Space Program. The mission brought back 94.7 kg of lunar samples that are still being tested today. This new research may spell change for other geological studies as well, using new techniques to overcome common problems with scientific dating.

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