From Sky & Telescope : “Two Impacts-Not Just One-May Have Formed The Moon”

From Sky & Telescope

October 14, 2021
Asa Stahl

In this image, the proposed hit-and-run collision is simulated in 3D, shown about an hour after impact. Theia, the impactor, barely escapes the collision. A. Emsenhuber / The University of Bern [Universität Bern](CH) / The Ludwig Maximilians University of Munich [Ludwig-Maximilians-Universität München](DE).

Theia Protoplanet slamming into Earth-Sci-News.com

Scientists have long thought that the Moon formed with a bang, when a protoplanet the size of Mars hit the newborn Earth. Evidence from Moon rocks and simulations back up this idea.

But a new study suggests that the protoplanet most likely hit Earth twice. The first time, the impactor (dubbed “Theia”) only glanced off Earth. Then, some hundreds of thousands of years later, it came back to deliver the final blow.

The study, which simulated the literally Earth-shattering impact thousands of times, found that such a “hit-and-run return” scenario could help answer two longstanding questions surrounding the creation of the Moon. At the same time, it might explain how Earth and Venus ended up so different.

The One-Two Punch

“The key issue here is planetary diversity,” says Erik Asphaug (The University of Arizona (US)), who led the study. Venus and Earth have similar sizes, masses, and distances from the Sun. If Venus is a “crushing hot-house,” he asks, “why is Earth so amazingly blue and rich?”

The Moon might hold the secret. Its creation was the last major episode in Earth’s formation, a catastrophic event that set the stage for the rest of our planet’s evolution. “You can’t understand how Earth formed without understanding how the Moon formed,” Asphaug explains. “They are part of the same puzzle.”

The new simulations, which were published in the October Journal of Planetary Sciences, put a few more pieces of that puzzle into place.

The first has to do with the speed of Theia’s impact. If Theia had hit our planet too fast, it would have exploded into an interplanetary plume of debris and eroded much of Earth. Yet if it had come in too slowly, the result would be a Moon whose orbit looks nothing like what we see today. The original impact theory doesn’t explain why Theia traveled at a just-right speed between these extremes.

“[This] new scenario fixes that,” says Matthias Meier (Natural History Museum, Switzerland), who was not involved in the study. Initially, Theia could have been going much faster, but the first impact would have slowed it down to the perfect speed for the second one.

The other problem with the original impact theory is that our Moon ought to be mostly made of primordial Theia. But Moon rocks from the Apollo missions show that Earth and the Moon have nearly identical compositions when it comes to certain kinds of elements. How could they have formed from two different building blocks?

“The canonical giant-impact scenario is really bad at solving [this issue],” Meier says (though others have tried).

A hit-and-run return, on the other hand, would enable Earth’s and Theia’s materials to mix more than in a single impact, ultimately forming a Moon chemically more similar to Earth. Though Asphaug and colleagues don’t quite fix the mismatch, they argue that more advanced simulations would yield even better results.

Earth vs. Venus

Resolving this aspect of the giant-impact theory would be no mean feat. But Asphaug’s real surprise came when he saw how hit-and-run impacts would have affected Venus compared to Earth.

“I first thought maybe there was a mistake,” he recalls.

The new simulations showed that the young Earth tended to pass on half of its hit-and-runners to Venus, while Venus accreted almost everything that came its way. This dynamic could help explain the drastic differences between the two planets: If more runners ended up at Venus, they would have enriched the planet in more outer solar system material compared to Earth. And since the impactors that escaped Earth to go on to Venus would have been the faster ones, each planet would have experienced generally different collisions.

This finding flips the original purpose of the study on its head. If Venus suffered more giant impacts than Earth, the question would no longer be “why does Earth have a moon?” but “why doesn’t Venus?”

Perhaps there was only one hit-and-run event, the one that made our Moon. Perhaps there were many, but for the same reason that Venus collected more impacts than Earth, it also accreted more destructive debris, obliterating any moon it already had. Or perhaps the last of Venus’ impacts was just particularly violent.

Finding out means taking a trip to Venus. That would provide “the next leap in understanding,” Meier says. If Earth and Venus both had hit-and-runs, for example, then the surface of Venus ought to be more like Earth’s than previously expected. If Venus has the same chemical similarities as the Moon and Earth, that would throw out the giant-impact theory’s last remaining problem.

“Getting samples from Venus,” Asphaug concludes, “is the key to answering all these questions.”

See the full article here .

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Sky & Telescope, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

“Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

From Curtin University (AU) : “Curtin researchers help date the youngest rocks ever found on the Moon”

From Curtin University (AU)

8 October 2021

Yasmine Phillips
Media Relations Manager (Work days: Tuesdays, Wednesdays and Thursdays)
Tel: +61 8 9266 9085
Mob: +61 401 103 877
yasmine.phillips@curtin.edu.au

Vanessa Beasley
Deputy Director
Tel: +61 8 9266 1811
Mob: +61 466 853 121
vanessa.beasley@curtin.edu.au

Curtin University researchers have helped to determine the age of the youngest rocks ever found on the Moon, as part of a global space mission that is working to refine the chronology of the entire Solar System.

China’s Chang’e-5 Moon landing in December 2020. Source: China National Space Administration [国家航天局](CN) Lunar Exploration and Space Engineering Center.

The new research, published in Science, determined the basaltic volcanic rocks, collected as part of China’s Chang’e-5 Moon landing in December 2020, were about two billion years old – or one billion years younger than those previously found on the Moon.

The rock samples were collected by the Chinese National Space Agency during the Chang’e-5 mission, which marked the first time any nation had collected rocks from the Moon since 1976.

Lead Australian author Professor Alexander Nemchin, from Curtin University’s Space Science and Technology Centre in the School of Earth and Planetary Sciences, said researchers determined the age of the lunar rock samples during remote sessions with the Beijing laboratory using large mass spectrometers that have helped revolutionise geology, similar to Curtin’s Sensitive High Resolution Ion Micro Probe Facility (SHRIMP).

“Previously, the youngest lunar basalt rocks collected as part of the Apollo and Luna missions, as well as lunar meteorites, were found to be older than about three billion years,” Professor Nemchin said.

“After analysing the chemistry of the new Moon rocks collected as part of China’s recent mission, we determined the new samples were about two billion years old, making them the youngest volcanic rocks identified on the Moon so far.

“This discovery puts Australia at the heart of efforts to internationalise scientific collaboration around China’s lunar exploration program, including samples returned from China’s Chang’e-5 mission and the upcoming Chang’e-6 Moon landing in 2024.”

Co-author Professor Gretchen Benedix, also from Curtin’s Space Science and Technology Centre, said the new results would provide researchers with more calibration points for cratering chronology, enabling them to derive more accurate and higher resolution ages across many planetary surfaces.

“These results confirm what experts had long predicted based on remotely obtained images of the Moon and raise further questions as to why these young basalts exist,” Professor Benedix said.

“The task will now turn to finding a mechanism that will explain how this relatively recent heating of the Moon may have supported the formation of basaltic magmas with temperatures exceeding 1000 degrees Celsius – and ultimately help researchers improve age dating of the entire Solar System.”

Professor Fred Jourdan from Curtin’s School of Earth and Planetary Sciences was also a co-author of this paper.

The research was carried out in collaboration with experts from the International Lunar and Planetary Research Center of China, The Beijing SHRIMP Center, The Australian National University, Washington University in St Louis, Notre Dame University and Brown University in the United States of America, the University of Colorado, Manchester University in the United Kingdom and the Natural History Museum in Sweden.

See the full article here .

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Curtin University (AU) (formerly known as Curtin University of Technology and Western Australian Institute of Technology) is an Australian public research university based in Bentley and Perth, Western Australia. The university is named after the 14th Prime Minister of Australia, John Curtin, and is the largest university in Western Australia, with over 58,000 students (as of 2016).

Curtin would like to pay respect to the indigenous members of our community by acknowledging the traditional owners of the land on which the Perth campus is located, the Wadjuk people of the Nyungar Nation; and on our Kalgoorlie campus, the Wongutha people of the North-Eastern Goldfields.

Curtin was conferred university status after legislation was passed by the Parliament of Western Australia in 1986. Since then, the university has been expanding its presence and has campuses in Singapore, Malaysia, Dubai and Mauritius. It has ties with 90 exchange universities in 20 countries. The University comprises five main faculties with over 95 specialists centres. The University formerly had a Sydney campus between 2005 & 2016. On 17 September 2015, Curtin University Council made a decision to close its Sydney campus by early 2017.

Curtin University is a member of Australian Technology Network (ATN), and is active in research in a range of academic and practical fields, including Resources and Energy (e.g., petroleum gas), Information and Communication, Health, Ageing and Well-being (Public Health), Communities and Changing Environments, Growth and Prosperity and Creative Writing.

It is the only Western Australian university to produce a PhD recipient of the AINSE gold medal, which is the highest recognition for PhD-level research excellence in Australia and New Zealand.

Curtin has become active in research and partnerships overseas, particularly in mainland China. It is involved in a number of business, management, and research projects, particularly in supercomputing, where the university participates in a tri-continental array with nodes in Perth, Beijing, and Edinburgh. Western Australia has become an important exporter of minerals, petroleum and natural gas. The Chinese Premier Wen Jiabao visited the Woodside-funded hydrocarbon research facility during his visit to Australia in 2005.

From Caltech: “Caltech-Led Lunar Trailblazer Mission Approved to Begin Final Design and Build”

From Caltech

December 02, 2020

Written by
Lori Dajose

Contact
Robert Perkins
(626) 395‑1862
rperkins@caltech.edu

After one year of preliminary design and several reviews, NASA has confirmed the Caltech-led Lunar Trailblazer mission to proceed to final design and build. Selected in June 2019 with planned flight system delivery in October 2022, the Lunar Trailblazer mission targets one of the most surprising discoveries of the decade: the presence of water on the Moon.

In this webinar presented by the Keck Institute for Space Studies, Caltech professor of planetary science Bethany Ehlmann presents the Lunar Trailblazer mission design and objectives. Credit: KISS/Caltech.
1:02:15

The mission is a collaboration led by principal investigator Bethany Ehlmann, Caltech professor of planetary science, and managed by JPL, which Caltech manages for NASA.

NASA JPL

Other key partners include spacecraft provider Lockheed Martin and the University of Oxford (UK), which provides one of Lunar Trailblazer’s two instruments.

“We’re excited to pioneer NASA’s use of small satellites to answer big planetary science questions,” says Ehlmann. “We expect Trailblazer will hugely advance our understanding of something we don’t fully understand: the water cycle on airless bodies. Given the importance of water on the Moon for future robotic and human missions, the Lunar Trailblazer mission team is excited to provide the critical basemaps that will guide this future exploration.”

The relatively tiny Trailblazer satellite, which will measure just 3.5 meters in length with its solar panels fully deployed, will spend over a year orbiting the Moon at a height of 100 kilometers, scanning it with two instruments: a visible-shortwave infrared imaging spectrometer built by JPL and a multispectral thermal imager built by the University of Oxford. These instruments will determine the amount and form of water on the Moon, which is not liquid but instead occurs as water ice in cold regions, as free molecules, or bound within minerals. As a NASA SIMPLEx (Small Innovative Missions for Planetary Exploration) program selection, Lunar Trailblazer achieves critical advancements for science as a lower-budget, ride-along mission.

“Lunar Trailblazer has a talented, multi-institutional team whose collective effort resulted in a successful formulation phase and confirmation review,” says Calina Seybold, the mission’s project manager at JPL. “I am thrilled that the team has earned the privilege of continuing to our final design and fabrication phase.”

A key partnership is with Lockheed Martin Space, based out of Denver, Colorado, which will design, integrate, and test the Lunar Trailblazer spacecraft. The company brings its expertise from another SIMPLEx mission called Janus, which will explore asteroids, as well as decades of planetary missions across the solar system.

Joshua Wood, Lunar Trailblazer spacecraft manager at Lockheed Martin, says he is excited for what lies ahead: “Passing this key decision point means we have the green flag to proceed with production on the spacecraft. I’m very excited to see all the big science this compact spacecraft will surely bring back to us.”

A key feature of Lunar Trailblazer is the large role for Caltech in executing the mission. In addition to Ehlmann’s leadership as PI, co-investigator James Dickson, manager of the Bruce Murray Laboratory for Planetary Visualization, will direct the science data system. Mission operations will be run out of Caltech’s IPAC, which brings long experience with space telescope science operations. Through a NASA-funded Student Collaboration Option, undergraduates from Caltech and nearby Pasadena City College are participating in mission communications and mission development, and will help staff operations. In addition to JPL, Lockheed Martin, University of Oxford (UK), and PCC, the other key mission partners are the Applied Physics Laboratory, Brown University, Northern Arizona University, and the University of Central Florida.

“Some of the big questions about water on the Moon are: Does it vary as a function of time of day and temperature? Is it bound in rock or mobile? Why do some shadowed regions host water ice while others are empty, and how much is there at the lunar surface?” says Ehlmann. “We look forward to answering these questions with Lunar Trailblazer.”

Learn more about the mission objectives, instruments, and team here: https://trailblazer.caltech.edu/

See the full article here .

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The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

Caltech campus

From Curiosity: “The Apollo 12 Mission Had a Curious Claim of Bacterial Life”

Curiosity Makes You Smarter

From From Curiosity

December 20, 2019
Elizabeth Howell

View, during NASA’s Apollo 12 mission, of the ‘Intrepid’ Lunar Module as it descends to the surface of the moon, November 19, 1969.
Interim Archives—Getty Images

Pieces of a craft that spent two years on the moon in the 1960s turned out to harbor something unexpected: bacteria. Did microbes successfully stow away for a moon mission and survive their return to Earth, or were they introduced during later testing? That’s one of the mysteries surrounding the Apollo 12 mission, which brought pieces of the Surveyor 3 robot back to Earth 50 years ago. Here are the latest theories about what happened.

Surviving Space?

The story begins with Apollo 12 astronaut Pete Conrad making a remarkable pinpoint landing on the Ocean of Storms in November 1969, fulfilling the mission objective to land within walking distance of the Surveyor 3 spacecraft that landed two years beforehand. Engineers were curious about how radiation in space might change a spacecraft over time, which is important if you want to design a durable spacecraft.

Astronauts Conrad and Alan Bean dutifully returned some pieces of Surveyor 3 back to Earth — the TV camera, some electrical cables, a sample scoop, and two pieces of aluminum tubing, according to NASA. What some scientists found in those samples has been the subject of Internet rumors ever since.

One research group recovered a little bit of the bacterium Streptococcus mitis, a harmless microorganism that lives in the human nose, throat, and mouth, in some foam within Surveyor 3’s newly returned camera. Surveyor 3 hadn’t been sterilized before going to the moon, and this research group supposed that microbes in the foam had survived the launch, the vacuum of space, and three years on the moon without any source for continuing life, such as water or nutrients. But there’s another explanation that you should consider first.

NASA

Earthly Contamination?

We’ve learned a lot about microbiology and about protecting spacecraft in the last 50 years, and the standards we use today are a lot higher than at the end of the 1960s. For example, the camera came back in a nylon duffel bag that was not airtight, unlike the lunar samples themselves.

“Some people associated with the curation of the Surveyor 3 materials have suggested that the one positive detection of life may be the result of accidental contamination of the material after it was returned to Earth,” NASA said in a statement on the experiment. And there are other explanations, too, including that perhaps the researchers had a false-positive result — that is, maybe they’d incorrectly detected microbes that weren’t actually there.

NASA noted another thing that probably would not be done today: “One of the implements being used to scrape samples off the Surveyor parts could have been laid down on a non-sterile laboratory bench, and then was used to collect surface samples for culturing. It is, therefore, quite possible that the microorganisms were transferred to the camera after its return to Earth.”

NASA

So what’s the verdict between the microbes surviving space for three years, or transferring through simple contamination? It’s hard to say for sure because we can’t repeat the experiment. However, the scientific community is leaning more towards the contamination hypothesis, according to a 2008 statement from one of NASA’s institutes. This hypothesis was also supported in a 2011 conference presentation with a team that included a NASA scientist. The agency tries to take it as a lesson learned when it prepares for missions to places like Mars. The Mars 2020 rover is being designed to search for signs of ancient life, and NASA needs to take every precaution to ensure any life they find is truly Martian.

Today, you can see the very camera that harbored these microbes at the Smithsonian Institution — a popular location for many space artifacts. The microbe mystery is a fun history lesson to consider and teaches us the importance of always checking claims carefully before accepting them at face value.

Surveyor III Television Camera
The television camera from the Surveyor III spacecraft was removed from Surveyor, about two-and-a-half years after the spacecraft landed, by the crew of Apollo 12 and returned to Earth. Smithsonian Ait and Space Museum

See the full article here .

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From AGU GeoSpace Blog: “Ancient Moon rock provides evidence of giant lunar impact 4.3 billion years ago”

From From AGU GeoSpace Blog

16 October 2019
Abigail Eisenstadt

Clast 3A refers to the area sampled from the anorthosite rock called 60016. The rock shown here was brought back during the Apollo 16 mission.
Credit: AGU.

An Apollo 16 lunar rock sample shows evidence of intense meteorite bombardment on the Moon 4.3 billion years ago, according to new research. The results provide new insights for the Moon’s early history, showing lunar impacts were common throughout the Moon’s formation than previously thought.

When the Moon first formed, its surface was covered in a sea of molten rock called the lunar magma ocean. This magma ocean eventually cooled and formed the rocks that make up the lunar crust and mantle.

A new study in AGU’s Journal of Geophysical Research: Planets analyzed a Moon rock from the Apollo 16 mission and found the rock cooled quicker than expected. The results suggest that 4.3 billion years ago a previously unidentified impact event forced the rock from the depths of the slowly cooling lunar crust to the surface.

“Something hit the Moon while the rocks were still at high temperatures, excavated the rock from depths in the lunar crust, and then it cooled quickly after that,” said Naomi Marks, a geochemist at Lawrence Livermore National Laboratory in Livermore, California and lead author of the new study.

Many planetary scientists had previously accepted the idea that the Moon had a relatively peaceful existence following its creation until the Late Heavy Bombardment, a period when the Moon was intensely pelted by meteorites and asteroids 4.0 billion to 3.8 billion years ago. But scientists have been questioning the accuracy of this theory. The new results add to growing evidence that the theory may be incorrect by identifying a major impact outside of the theory’s timeframe, according to the study’s authors.

“We are fairly confident that that the age is recording an impact, which means that there were significant impacts outside of the Late Heavy Bombardment period,” Marks said.

Understanding ancient lunar impacts could help scientists uncover more information about the early Moon’s formation and its surroundings.

Forming rocks from magma

The Moon is thought to have originated from debris created by a collision between an ancient Mars-sized planet and Earth. During its initial period of formation, the Moon’s surface was an ocean of magma. Eventually, heavier elements began to sink to the depths of the ocean, forming the solid lunar core around 4.4 billion years ago. Then the outer layer comprised of lighter material began to rise to the top and cool. This formation of the lunar crust is estimated to have taken between 10 million and 250 million years.

Studying the lunar crust allows scientists to learn more about the Moon’s origins and evolution. One type of lunar surface rock, called anorthosites, are responsible for the Moon’s bright white color and were once thought to be the oldest rocks on the lunar surface.

In the new study, Marks and her colleagues wanted to use anorthosites to estimate how long it took for the lunar magma ocean to cool and solidify into rocks. They took a sample from a previously unexamined anorthosite collected by the Apollo 16 mission and analyzed isotopes produced by the radioactive decay of elements within the rock to determine when it cooled to certain temperatures.

They found the rock went from around 855 degrees Celsius (1,571 degrees Fahrenheit) to roughly 250 degrees Celsius (482 degrees Fahrenheit) within a few thousand years – an unusually quick cooling rate in the scheme of other planetary timescales. The rapid cooling indicates a major impact likely propelled rock out of the lower crust to the surface, where it rapidly cooled into anorthosite alongside other rocks, according to the authors.

The study provides good evidence for a large impact on the Moon 4.3 billion year ago, adding to many decades of research on lunar chronology, said Kevin McKeegan, a planetary scientist at the University of California, Los Angeles in Los Angeles, California, who was unaffiliated with the study.

Evidence for the ancient lunar impact reveals how tumultuous the Moon’s early period was, helping scientists understand more about its formation and composition, according to Marks.

See the full article here .

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GeoSpace is a blog on Earth and space science, managed by AGU’s Public Information staff. The blog features posts by AGU writers and guest contributors on all sorts of relevant science topics, but with a focus on new research and geo and space sciences-related stories that are currently in the news.

Do you have ideas on topics we should be covering? Would you like to contribute a guest post to the blog? Contact Peter Weiss at pweiss@agu.org.