The Moon Once Had An Atmosphere

A new study shows that an atmosphere was produced around the ancient Moon, 3 to 4 billion years ago, when intense volcanic eruptions spewed gases above the surface faster than they could escape to space. The study was published in Earth and Planetary Science Letters.

When one looks up at the Moon, dark surfaces of volcanic basalt can be easily seen to fill large impact basins. Those seas of basalt, known as maria, erupted while the interior of the Moon was still hot and generating magmatic plumes that sometimes breached the lunar surface and flowed for hundreds of kilometers. Analyses of Apollo samples indicate those magmas carried gas components, such as carbon monoxide, the ingredients for water, sulfur, and other volatile species.

In new work, Dr. Debra H. Needham, Research Scientist of NASA Marshall Space Flight Center, and Dr. David A. Kring, Senior Staff Scientist, at the Lunar and Planetary Institute, calculated the amounts of gases that rose from the erupting lavas as they flowed over the surface and showed that those gases accumulated around the Moon to form a transient atmosphere. The atmosphere was thickest during the peak in volcanic activity about 3.5 billion years ago and, when created, would have persisted for about 70 million years before being lost to space.

The two largest pulses of gases were produced when lava seas filled the Serenitatis and Imbrium basins about 3.8 and 3.5 billion years ago, respectively. The margins of those lava seas were explored by astronauts of the Apollo 15 and 17 missions, who collected samples that not only provided the ages of the eruptions, but also contained evidence of the gases produced from the erupting lunar lavas.

This new picture of the Moon has important implications for future exploration. The analysis of Needham and Kring quantifies a source of volatiles that may have been trapped from the atmosphere into cold, permanently shadowed regions near the lunar poles and, thus, may provide a source of ice suitable for a sustained lunar exploration program. Volatiles trapped in icy deposits could provide air and fuel for astronauts conducting lunar surface operations and, potentially, for missions beyond the Moon.

The new research was initiated from the LPI-Johnson Space Center’s Center for Lunar Science and Exploration, led by Kring and supported by NASA’s Solar System Exploration Research Virtual Institute. Needham is a former postdoctoral researcher at the LPI.

Asteroid Tracking Network Observes Close Approach

On Oct. 12 EDT (Oct. 11 PDT), a small asteroid designated 2012 TC4 will safely pass by Earth at a distance of approximately 26,000 miles (42,000 kilometers). This is a little over one tenth the distance to the Moon and just above the orbital altitude of communications satellites. This encounter with TC4 is being used by asteroid trackers around the world to test their ability to operate as a coordinated international asteroid warning network.

2012 TC4 is estimated to be 50 to 100 feet (15 to 30 meters) in size. Orbit prediction experts say the asteroid poses no risk of impact with Earth. Nonetheless, its close approach to Earth is an opportunity to test the ability of a growing global observing network to communicate and coordinate its optical and radar observations in a real scenario.

This asteroid was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii in 2012. Pan-STARRS conducts a near-Earth object (NEO) survey funded by NASA’s NEO Observations Program, a key element of NASA’s Planetary Defense Coordination Office. However, 2012 TC4 traveled out of the range of asteroid-tracking telescopes shortly after it was discovered.

Based on the observations they were able to make in 2012, asteroid trackers predicted that it should come back into view in the fall of 2017. Observers with the European Space Agency and the European Southern Observatory were the first to recapture 2012 TC4, in late July 2017, using one of their large 8-meter aperture telescopes.Since then, observers around the world have been tracking the object as it approaches Earth and reporting their observations to the Minor Planet Center.

This “test” of what has become a global asteroid-impact early-warning system is a volunteer project, conceived and organized by NASA-funded asteroid observers and supported by the NASA Planetary Defense Coordination Office (PDCO).

As explained by Michael Kelley, program scientist and NASA PDCO lead for the TC4 observation campaign, “Asteroid trackers are using this flyby to test the worldwide asteroid detection and tracking network, assessing our capability to work together in response to finding a potential real asteroid-impact threat.”

No asteroid currently known is predicted to impact Earth for the next 100 years.

Asteroid TC4’s closest approach to Earth will be over Antarctica at 1:42 AM EDT on Oct. 12 (10:42 p.m. PDT on Oct. 11). Tens of professionally run telescopes across the globe will be making ground-based observations in wavelengths from visible to near-infrared to radar. Amateur astronomers may contribute more observations, but the asteroid will be very difficult for backyard astronomers to see, as current estimates are that it will reach a visual magnitude of only about 17 at its brightest, and it will be moving very fast across the sky.

Many of the observers who are participating in this exercise are funded by NASA’s NEO Observations Program, but observers supported by other countries’ space agencies and space institutions around the world are now involved in the campaign.

Vishnu Reddy, an assistant professor at the University of Arizona’s Lunar and Planetary Laboratory in Tucson, is leading the 2012 TC4 campaign. Reddy is principal investigator for a NASA-funded near-Earth asteroid characterization project. “This campaign is a team effort that involves more than a dozen observatories, universities and labs around the globe so we can collectively learn the strengths and limitations of our near-Earth object observation capabilities,” he said. “This effort will exercise the entire system, to include the initial and follow-up observations, precise orbit determination, and international communications.”

In September, asteroid observers were able to conduct a “pre-test” of coordinated tracking of the close approach of a much larger asteroid known as 3122 Florence. Florence, one of the largest known NEOs, at 2.8 miles (4.5 kilometers) in size, passed by Earth on Sept. 1 at 18 times the distance to the Moon. Coordinated observations of this asteroid revealed, among other things, that Florence has two moons.

Astronomers Use IAC Instrument To Probe The Origins Of Cosmic Rays

In November 1572 a supernova explosion was observed in the direction of the constellation of Cassiopeia, and its most famous observer was Tycho Brahe, one of the founders of modern observational astronomy. The explosion produced an expanding cloud of superhot gas, a supernova remnant which was rediscovered in 1952 by British radioastronomers, confirmed by visible photographs from Mount Palomar observatory, California, in the 1960’s, and a spectacular image was taken in X-rays by the Chandra satellite observatory in 2002. Astronomers use supernova remnants to explore high energy physics in interstellar space.

In an article to be published in the Astrophysical Journal a team from 7 countries, including researchers at the Instituto de Astrofísica de Canarias (IAC), has observed the Tycho supernova remnant with GHaFaS, a sophisticated instrument from the IAC, mounted on the 4.2m William Herschel Telescope (WHT) at the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands). Their aim was to explore the hypothesis that the cosmic rays, high energy sub-atomic particles which continually bombard the Earth’s outer atmosphere, originate in these highly energetic gas clouds. GHaFaS allows astronomers to observe the emission from ionized hydrogen across wide fields, giving a map of the velocity structure within an object in fine detail.

They mapped a sizeable portion of the Tycho remnant cloud, including a prominent bright filament, and showed that the hydrogen line emitted from the filament shows a much bigger spread of velocities than can be explained from the temperature of the gas. In fact they measured two components of emission, one with a large velocity spread, and another with an even larger spread. They showed that the only way for the emission to show these characteristics is if there is a mechanical mechanism in the cloud producing high energy particles. Supernova remnants have long been considered a probable source of the cosmic rays which pour onto the outer atmosphere of the Earth, but this is the first time that clear evidence for an acceleration mechanism has been produced. Cosmic rays have energies much higher than those produced in even the biggest particle accelerators on Earth (such as CERN), and their study is important not only for astrophysics but for particle physics.

“These results could not have been produced by any of the other spectrographs on major telescopes in the world” says Joan Font, one of the authors of the article, and the person responsible for the operations of GHaFaS. “Our instrument has a unique combination of high velocity resolution, wide field, and good angular resolution, and this combination was required for the Tycho project”. These observations are a first step towards a fuller understanding of the cosmic ray acceleration mechanism in supernova remnants. “We should be able to combine these results with observations already taken using the OSIRIS narrow band imager on the 10.4m Gran Telescopio CANARIAS (GTC) to determine the efficiency of acceleration of the cosmic rays” says John Beckman, another IAC researcher and a co-author on the paper.

Mars Study Yields Clues To Possible Cradle Of Life

The discovery of evidence for ancient sea-floor hydrothermal deposits on Mars identifies an area on the planet that may offer clues about the origin of life on Earth.

A recent international report examines observations by NASA’s Mars Reconnaissance Orbiter (MRO) of massive deposits in a basin on southern Mars. The authors interpret the data as evidence that these deposits were formed by heated water from a volcanically active part of the planet’s crust entering the bottom of a large sea long ago.

“Even if we never find evidence that there’s been life on Mars, this site can tell us about the type of environment where life may have begun on Earth,” said Paul Niles of NASA’s Johnson Space Center, Houston. “Volcanic activity combined with standing water provided conditions that were likely similar to conditions that existed on Earth at about the same time — when early life was evolving here.”

Mars today has neither standing water nor volcanic activity. Researchers estimate an age of about 3.7 billion years for the Martian deposits attributed to seafloor hydrothermal activity. Undersea hydrothermal conditions on Earth at about that same time are a strong candidate for where and when life on Earth began. Earth still has such conditions, where many forms of life thrive on chemical energy extracted from rocks, without sunlight. But due to Earth’s active crust, our planet holds little direct geological evidence preserved from the time when life began. The possibility of undersea hydrothermal activity inside icy moons such as Europa at Jupiter and Enceladus at Saturn feeds interest in them as destinations in the quest to find extraterrestrial life.

Observations by MRO’s Compact Reconnaissance Spectrometer for Mars (CRISM) provided the data for identifying minerals in massive deposits within Mars’ Eridania basin, which lies in a region with some of the Red Planet’s most ancient exposed crust.

“This site gives us a compelling story for a deep, long-lived sea and a deep-sea hydrothermal environment,” Niles said. “It is evocative of the deep-sea hydrothermal environments on Earth, similar to environments where life might be found on other worlds — life that doesn’t need a nice atmosphere or temperate surface, but just rocks, heat and water.”

Niles co-authored the recent report in the journal Nature Communications with lead author Joseph Michalski, who began the analysis while at the Natural History Museum, London, and co-authors at the Planetary Science Institute in Tucson, Arizona, and the Natural History Museum.

The researchers estimate the ancient Eridania sea held about 50,000 cubic miles (210,000 cubic kilometers) of water. That is as much as all other lakes and seas on ancient Mars combined and about nine times more than the combined volume of all of North America’s Great Lakes. The mix of minerals identified from the spectrometer data, including serpentine, talc and carbonate, and the shape and texture of the thick bedrock layers, led to identifying possible seafloor hydrothermal deposits. The area has lava flows that post-date the disappearance of the sea. The researchers cite these as evidence that this is an area of Mars’ crust with a volcanic susceptibility that also could have produced effects earlier, when the sea was present.

The new work adds to the diversity of types of wet environments for which evidence exists on Mars, including rivers, lakes, deltas, seas, hot springs, groundwater, and volcanic eruptions beneath ice.

“Ancient, deep-water hydrothermal deposits in Eridania basin represent a new category of astrobiological target on Mars,” the report states. It also says, “Eridania seafloor deposits are not only of interest for Mars exploration, they represent a window into early Earth.” That is because the earliest evidence of life on Earth comes from seafloor deposits of similar origin and age, but the geological record of those early-Earth environments is poorly preserved.

The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, built and operates CRISM, one of six instruments with which MRO has been examining Mars since 2006. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the project for the NASA Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver built the orbiter and supports its operations.

Meteorite Tells Us That Mars Had A Dense Atmosphere 4 Billion Years Ago

Exploration missions have suggested that Mars once had a warm climate, which sustained oceans on its surface. To keep Mars warm requires a dense atmosphere with a sufficient greenhouse effect, while the present-day Mars has a thin atmosphere whose surface pressure is only 0.006 bar, resulting in the cold climate it has today. It has been a big mystery as to when and how Mars lost its dense atmosphere.

An old meteorite has been known to contain the ancient Martian atmosphere. The researchers simulated how the composition of the Martian atmosphere changed throughout history under various conditions. By comparing the results to the isotopic composition of the trapped gas, the researchers revealed how dense the Martian atmosphere was at the time when the gas became trapped in the meteorite.

The research team concluded that Mars had a dense atmosphere 4 billion years ago. The surface air pressure at the time was at least 0.5 bar and could have been much higher. Because Mars had its magnetic field about 4 billion years ago and lost it, the result suggests that stripping by the solar wind is responsible for transforming Mars from a warm wet world into a cold desert world.

NASA’s MAVEN spacecraft is orbiting Mars to explore the processes that removed the Martian atmosphere. The Japan Aerospace Exploration Agency (JAXA) is planning to further observe the removal processes by the Martian Moons eXploration (MMX) spacecraft. These missions will reveal how the dense atmosphere on ancient Mars predicted in this study was removed over time.

New Light Shed On How Earth And Mars Were Created

Analysing a mixture of earth samples and meteorites, scientists from the University of Bristol have shed new light on the sequence of events that led to the creation of the planets Earth and Mars.

Planets grow by a process of accretion — a gradual accumulation of additional material — in which they collisionally combine with their neighbours.

This is often a chaotic process and material gets lost as well as gained.

Massive planetary bodies impacting at several kilometres per second generate substantial heat which, in turn, produces magma oceans and temporary atmospheres of vaporised rock.

Before planets get to approximately the size of Mars, gravitational attraction is too weak to hold onto this inclement silicate atmosphere.

Repeated loss of this vapour envelope during continued collisional growth causes the planet’s composition to change substantially.

Dr Remco Hin from the University of Bristol’s School of Earth Sciences, led the research which is published today in Nature.

He said: “We have provided evidence that such a sequence of events occurred in the formation of the Earth and Mars, using high precision measurements of their magnesium isotope compositions.

“Magnesium isotope ratios change as a result of silicate vapour loss, which preferentially contains the lighter isotopes. In this way, we estimated that more than 40 per cent of the Earth’s mass was lost during its construction.

“This cowboy building job, as one of my co-authors described it, was also responsible for creating the Earth’s unique composition.”

The research was carried out in an effort to resolve a decades long debate in Earth and planetary sciences about the origin of distinctive, volatile poor compositions of planets.

Did this result from processes that acted in the mixture of gas and dust in the nebula of the earliest solar system or is it consequence of their violent growth?

Researchers analysed samples of the Earth together with meteorites from Mars and the asteroid Vesta, using a new technique to get higher quality (more accurate and more precise) measurements of magnesium isotope ratios than previously obtained.

The main findings are three-fold:

Earth, Mars and asteroid Vesta have distinct magnesium isotope ratios from any plausible nebula starting materials

The isotopically heavy magnesium isotope compositions of planets identify substantial (~40 per cent) mass loss following repeated episodes of vaporisation during their accretion

This slipshod construction process results in other chemical changes during growth that generate the unique chemical characteristics of Earth.

Dr Hin added: “Our work changes our views on how planets attain their physical and chemical characteristics.

“While it was previously known that building planets is a violent process and that the compositions of planets such as Earth are distinct, it was not clear that these features were linked.

“We now show that vapour loss during the high energy collisions of planetary accretion has a profound effect on a planet’s composition.

“This process seems common to planet building in general, not just for Earth and Mars, but for all planets in our Solar System and probably beyond, but differences in the collision histories of planets will create a diversity in their compositions.”

Supersonic Gas Streams Left Over From The Big Bang Drive Massive Black Hole Formation

An international team of researchers has successfully used a super-computer simulation to recreate the formation of a massive black hole from supersonic gas streams left over from the Big Bang. Their study, published in this week’s Science, shows this black hole could be the source of the birth and development of the largest and oldest super-massive black holes recorded in our Universe.

“This is significant progress. The origin of the monstrous black holes has been a long-standing mystery and now we have a solution to it,” said author and Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Principal Investigator Naoki Yoshida.

Recent discoveries of these super-massive black holes located 13 billion light years away, corresponding to when the universe was just five per cent of its present age, pose a serious challenge to the theory of black hole formation and evolution. The physical mechanisms that form black holes and drive their growth are poorly understood.

Theoretical studies have suggested these black holes formed from remnants of the first generation of stars, or from a direct gravitational collapse of a massive primordial gas cloud. However, these theories either have difficulty in forming super-massive black holes fast enough, or require very particular conditions.

Yoshida and JSPS Overseas Research Fellow Shingo Hirano, currently at the University of Texas at Austin, identified a promising physical process through which a massive black hole could form fast enough. The key was incorporating the effect of supersonic gas motions with respect to dark matter. The team’s super-computer simulations showed a massive clump of dark matter had formed when the universe was 100 million years old. Supersonic gas streams generated by the Big Bang were caught by dark matter to form a dense, turbulent gas cloud. Inside, a protostar started to form, and because the surrounding gas provided more than enough material for it to feed on, the star was able to grow extremely big in a short amount of time without releasing a lot of radiation.

“Once reaching the mass of 34,000 times that of our Sun, the star collapsed by its own gravity, leaving a massive black hole. These massive black holes born in the early universe continued to grow and merge together to become a supermassive black hole,” said Yoshida.

“The number density of massive black holes is derived to be approximately one per a volume of three billion light-years on a side — remarkably close to the observed number density of supermassive black holes,” said Hirano.

The result from this study will be important for future research into the growth of massive black holes. Especially with the increased number of black hole observations in the far universe that are expected to be made when NASA’s James Webb Space Telescope is launched next year.