Moon Archives

April 25, 2012December 23, 2015 by Nancy Atkinson

Ancient Asteroids Kept Pelting Earth in a ‘Late-Late’ Heavy Bombardment

This is an artist’s depiction of a 10-kilometer (6-mile) diameter asteroid striking the Earth. New evidence in Australia suggests an asteroid 2 to 3 times larger than this struck Earth early in its life. Credit: Don Davis/Southwest Research Institute.

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Even though the Late Heavy Bombardment is somewhat of a controversial idea, new research has revealed this period of impacts to the Earth-Moon system may have lasted much longer than originally estimated and well into the time when early life was forming on Earth. Additionally, this “late-late” period of impacts — 3.8 billion to 2.5 billion years ago — was not for the faint of heart. Various blasts may have rivaled those that produced some of the largest craters on the Moon, and could have been larger than the dinosaur-killing impact that created the Chicxulub crater 65 million years ago.

“Our work provides a rationale that the last big impacts hit over an extended time,” said William Bottke principal investigator of the impact study team at the NASA Lunar Science Institute’s Center of Lunar Origin and Evolution (CLOE), based at the Southwest Research Institute (SwRI) in Boulder, Colorado.

The evidence for these prodigious impacts comes from bead-like impact ‘spherules’ found in millimeter- to centimeter-thick rock layers on Earth and date from the Archean period of Earth’s history, more recent than the estimated LHB period of 4.1 to 3.8 billion years ago.

“The beds speak to an intense period of bombardment of Earth,” Bottke said. “Their source long has been a mystery.”

The circles seen in the image above are all formerly molten droplets ejected into space when an asteroid struck the Earth about 2.56 billion years ago. The droplets returned to Earth and were concentrated at the base of the Reivilo layer in South Africa.

The spherules still contain substantial extraterrestrial material, such as iridium (176 parts per million), which rules out alternative sources for the spherules, such as volcanoes, according to Bruce Simonson, a geologist from the Oberlin College and Conservatory who has studied these ancient layers for decades.

The timing of these impacts also coincides with a record of large lunar craters being created more recently than 3.8-billion years ago.

At least 12 spherule beds deposited between 3.47 and 1.7 billion years ago have been found in protected areas on Earth, such as in shales deposited on the seafloor below the reach of waves.

From these beds, the team found evidence of approximately 70 impacts on Earth during this time period that were likely larger than the Chicxulub impact.

In their paper, which was published in Nature, the team created a computer model of the ancient main asteroid belt and tracked what would have happened when the orbits of the giant planets changed. They extended the work of the Nice Model, which supports the theory that Jupiter, Saturn, Uranus and Neptune formed in different orbits nearly 4.5 billion years ago and migrated to their current orbits about 4 billion years ago, triggering a solar system-wide bombardment of comets and asteroids called known as the LHB.

postlc-solar-system — This image shows a representation of how the giant planets have migrated to the current orbits, destabilizing the extension of the primordial asteroid belt closest to Mars. This drove numerous big impactors onto orbits where they could hit the terrestrial planets, though over a long enough time span that this drawn-out barrage may have lasted more than a billion years. The frequency of these impacts on Earth was enough to reproduce the known impact spherule beds. Image Courtesy David Kring, Center for Lunar Science and Exploration, and the Lunar and Planetary Institute

The new computer model shows that the innermost portion of the asteroid belt could have become destabilized, delivering numerous big impacts to Earth and Moon over longer time periods.

Have there been any previous indications about this period of impacts?

“The problem is that we have almost no Archean rocks,” Bottke told Universe Today. “The oldest terrestrial craters, Sudbury and Vredefort, are 1.85 and 2.02 billion years old. The spherule beds are our only window into impacts prior to this time.”

Also, Bottke said, the number of people who look for impact spherules is almost equally scarce. “People such as Bruce Simonson, Don Lowe, Gary Byerly, and Frank Kyte, have been carrying on a long, lonely quest to try to get people to consider the implications of their work, which are deeply profound, in my opinion,” Bottke said.

As for finding evidence of this later period of impacts on the Moon, Bottke said the problem there is the lack of solid ages for most impact events.

“This means it is difficult say anything definitive about the timing of major impacts,” Bottke said. “We are working this problem now with Michelle Kirchoff, who is counting craters on top of large lunar craters. This can be done now that we have LRO data.” (Listen to a podcast interview of Kirchoff on the 365 Days of Astronomy.)

Still, Bottke said, without using “fancy dynamics,” they can address some issues.

“Studies in the post-Apollo era suggested that the Moon has four 160-300 km craters that formed after Orientale, whose age is 3.7-3.8 billion years ago and (i.e., K/T-sized events or larger),” he said. “Crater counts from the Galileo mission and Apollo-era geologic analyses suggest at least one of these events took place near 3.2-3.5 billion years ago. If we account for the gravitational cross section of the planets, we know that for every lunar event, we should get about 20 on the Earth. So, from this argument alone, one should get a lot of big impacts on the Earth after the formation of Orientale.”

The new study fits with the available constraints about impacts on the Moon as well as finding the right distribution of spherule beds on Earth.

The best way to confirm everything, however, Bottke said, would be if more lunar rocks from various locations were available for study.

Read the team’s paper in Nature.

Further reading:
Press release from SwRI.
NLSI press release

April 24, 2012December 23, 2015 by Jason Major

Lunar Satellite Reveals Apollo 16 Remains

LROC image of the Apollo 16 site showing the Orion LM. (NASA/GSFC/Arizona State University)

NASA’s Lunar Reconnaissance Orbiter (LRO) made a low pass over the Apollo 16 site last fall, capturing images of the leftovers from John Young and Charlie Duke’s 1972 exploration of the Descartes Highlands. The video above takes us on a tour of the Apollo 16 site from lunar orbit, and includes audio from the original communications and some very nice comparative photos and video clips showing the same features from ground level.

The goal of Apollo 16 was to explore for the first time a lunar highlands location, and collect samples of what were initially thought to be volcanic rocks. The rocks were believed to be of a different material than what was collected during previous missions.

As it turned out, the rocks collected by Duke and Young weren’t volcanic in origin at all; they ended up being breccias — cemented-together chunks ejected from ancient cratering events hundreds of miles away.

Apollo 16 also set up various experiment packages to study lunar geology, magnetism and the solar wind. The Lunar Roving Vehicle (LRV) allowed Young and Duke to travel across a much wider area than they would have otherwise been able to on foot. It was the second mission to use an LRV, and the rover — as well as its tracks — are still there today, looking exactly as they did when they were left 40 years ago.

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The Apollo 16 ascent stage lifted off from the lunar surface on the evening of April 23, 1972 and docked with the Command Module containing Ken Mattingly. The following day the astronauts began their trip back to Earth, completing the 250,000-mile traverse three days later on April 27.

The Moon would be visited again in December of that same year during Apollo 17, the last mission of the program and the last time that humans would walk on the surface of another world. Now, 40 years later, satellites orbiting the Moon take pictures of what was left behind by these historic events. Perhaps someday soon the sites will be visited from ground level… maybe even by a new generation of astronauts.

Apollo16_pan — Panorama of the Descartes Highlands site made from 3 Hasselblad film image scans combined together. (NASA/JSC/J. Major)

Read more about this on Arizona State University’s LROC site, and explore the full-frame Narrow-Angle Camera image from the LROC here.

Video: NASA/GSFC/Arizona State University

April 24, 2012December 23, 2015 by Jason Major

The Family that Went to the Moon

A picture of a photograph: the family photo that Charlie Duke left on the Moon on April 23, 1972. (NASA)

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Well, the family photo, anyway.

On April 23, 1972, Apollo 16 astronauts Charlie Duke and John Young embarked on the third and final EVA of the mission, exploring the Descartes Highlands via Lunar Roving Vehicle. During the EVA, before setting up a Solar Wind Collector, Duke placed a small family photo he had brought along onto the lunar surface and snapped a few photos of it with his Hasselblad film camera. This is one of the photos.

The portrait shows Charlie, his wife Dorothy, and their two sons Charles and Thomas. It looks like they are sitting on a bench in the summertime.

The family photo, gingerly wrapped in clear plastic and slightly crumpled from being stashed in the pocket of a space suit, was left on the Moon. It presumably still sits there today, just inches away from Charlie’s boot print — which, presumably, is also there.

At the time of this writing it’s been exactly 40 years to the day that this photo was taken.

Image: NASA/JSC scan

I came across this image while looking through the Project Apollo Image Archive for some relevant images from the Apollo 16 mission. Amid scans of Hasselblad photos showing lunar samples, experiments and scenes from LRV jaunts, which are all fascinating in their own right, I came across this poignant image and couldn’t resist sharing it. To know that a family photo is resting upon the surface of another world is nothing short of amazing… while the missions to the Moon were a testament to human endeavor, it’s small things like this that remind us of the people that made it all possible.

April 23, 2012December 23, 2015 by Nancy Atkinson

Join the Million Crater Challenge

Like a challenge? Right now you can join in a contest to mark a million craters, as part of the Moon Mappers project. “Our challenge to you is to try and observe 1 million craters on the Moon before the full Moon again rises in the evening sky on May 5,” said Dr. Pamela Gay, who leads the Cosmoquest program of citizen science project. “Help us ‘illuminate’ the Moon with new scientific discoveries one crater at a time.”

As an enticement to join in, there are prizes!

There will be prizes for the ten CosmoQuest community members who make the observations closest to each interval of 100,000, and for 10 additional randomly selected community members who participate in this challenge. Prizes include Surly Amy pendants, Astrosphere posters, and Lunar Reconnaissance Orbiter lithographs.

Are there a million craters on the Moon? Dr. Gay said that with LRO, craters the size on 1 meter can be seen. But for Moon Mappers, participants are asked to identify craters nine meters in diameter. “There are literally millions of craters at that size,” she said.

Moon Mappers is not only fun, but your contributions help build a new scientific understanding of the Moon. The Moon Mappers team has already published their first scientific paper based on the work done by citizen scientists, so help them keep going to discover as much as we can about the Moon.

Check out Moon Mappers!

April 23, 2012December 23, 2015 by Jason Major

Earthrise, Revisited

The first color photo of Earth taken from orbit around the Moon. (NASA)

On December 24, 1968, Apollo 8 astronauts Frank Borman, William Anders and Jim Lovell were the first humans to witness an Earthrise as our home planet came up over the lunar horizon. The photos they captured were the first of their kind, instantly inspiring the imaginations of millions and highlighting the beauty and fragility of our world.

Now, NASA has used modern satellite data to recreate the scenes that the Apollo 8 astronauts saw 44 years ago and combined them with their historic photographs to present a new “Earthrise”… version 2.0.

Created in recognition of Earth Day 2012, the Earthrise animation was made from data acquired by NASA’s Lunar Reconnaissance Orbiter’s laser altimeter, as well as the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra Earth-observing satellite.

“This visualization recreates for everyone the wondrous experience of seeing Earth from that privileged viewpoint,” says LRO Project Scientist Rich Vondrak of NASA’s Goddard Space Flight Center.

Animator Ernie Wright recreated the scene using Apollo mission reports and photos taken by the crew. The audio is a recording of original communication from the astronauts.

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“I think the one overwhelming emotion that we had was when we saw the earth rising in the distance over the lunar landscape… it makes us realize that we all do exist on one small globe. For from 230,000 miles away it really is a small planet.”

— Frank Borman, Apollo 8 Commander

Read the release on the NASA LRO site here.

Video: NASA/GSFC

April 16, 2012December 23, 2015 by Nancy Atkinson

Beautiful Image: The Moon as Seen from the Space Station

The Moon hovers Earth's atmosphere as seen from the International Space Station. Credit: NASA/ESA/Expedition 30 crew

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A lovely view for the start of your week: The Moon and Earth’s atmosphere as seen from the International Space Station, taken by a member of the current Expedition 30 crew. See more images from the crew here.

April 14, 2012April 26, 2016 by Jason Major

Scientists Suggest Evidence of Recent Lunar Volcanism

There may be a volcanic vent on the central peak of Tycho crater, according to an Indian research team. (Image: NASA Goddard/Arizona State University)

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A team of researchers at India’s Physical Research Laboratory (PRL) claims it has found evidence of relatively recent volcanic activity on the Moon, using data from NASA’s Lunar Reconnaissance Orbiter and the Chadrayaan-1 spacecraft. According to the findings the central peak of Tycho crater contains features that are volcanic in origin, indicating that the Moon was geologically active during the crater’s formation 110 million years ago.

In an article by the Deccan Herald, a Bangalore-based publication, the PRL researchers claim that vents, lava channels and solidified flows of inner crustal material found within Tycho were made as recently as 100 million years ago — after the creation of the crater.

This could indicate that there was pre-existing volcanic activity within the Moon at the site of the Tycho impact, lending credence to the idea that the Moon was recently geologically active.

In addition, large boulders ranging in size from 33 meters to hundreds of yards across have been spotted on Tycho’s central peaks by LRO, including one 400-foot (120-meter) -wide specimen nestled atop the highest summit. How did such large boulders get there and what are they made of?

Tycho Boulder — A 400-foot-wide boulder within the central peak of Tycho. (NASA/GSFC/LROC)

The researchers hint that they may also be volcanic in origin.

“A surprise findings revealed the presence of large boulders–about 100 meter in size –on top of the peak. Nobody knew how did they reach the top,” said Prakash Chauhan, a PRL scientist.

Without further studies it’s difficult to determine the exact origin and ages of these lunar formations. The team awaits future research by Chandrayaan-II, which will examine the Moon from orbit as well as land a rover onto the lunar surface. Chandrayaan-II is expected to launch in early 2014.

The PRL team’s findings were published in the April 10 issue of Current Science.

Read the article in the Deccan Herald here.

April 12, 2012April 26, 2016 by Jason Major

What’s the Moon Made Of? Earth, Most Likely.

An impact between a Mars-sized protoplanet and early Earth is the most widely-accepted origin of the Moon. Did smaller impacts seed the formation of continents? (NASA/JPL-Caltech)

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Recent research on lunar samples has shown that the Moon may be made of more Earth than green cheese — if by “green cheese” you mean the protoplanet impactor that was instrumental in its creation.

It’s an accepted hypothesis that Earth’s moon was created during an ancient, violet collision between our infant planet and a Mars-sized world called Theia, an event that destroyed Theia and sent part of Earth’s crust and upper mantle into orbit as a brief-lived ring of molten material. This material eventually coalesced to form the Moon, and over the next 4.5 billion years it cooled, became tidally locked with Earth, accumulated countless craters and gradually drifted out to the respectable distance at which we see it today.

Theia’s remains were once assumed to have been a major contributor to the material that eventually formed the Moon. Lunar samples, however, showed that the ratio of oxygen isotopes on the Moon compared to Earth were too similar to account for such a formation. Now, further research by a team led by scientists from The University of Chicago shows that titanium isotopes — an element much more refractive than oxygen — are surprisingly similar between the Moon and Earth, further indicating a common origin.

“After correcting for secondary effects associated with cosmic-ray exposure at the lunar surface using samarium and gadolinium isotope systematics, we find that the ⁵⁰Ti/⁴⁷Ti ratio of the Moon is identical to that of the Earth within about four parts per million, which is only 1/150 of the isotopic range documented in meteorites,” wrote University of Chicago geophysicist Junjun Zhang, lead author of the paper published in the journal Nature Geoscience on March 25.

If the Moon is more Earth than Theia, then what happened to the original impacting body? Perhaps it was made of heavier stuff that sunk deeper into the Moon, or was assimilated into Earth’s mantle, or got lost to space… only more research will tell.

But for now, you can be fairly sure that when you’re looking up at the Moon you’re seeing a piece of Earth, the cratered remnants of a collision that took place billions of years ago.

See the team’s paper here.

Image credit: NASA / JPL-Caltech

April 10, 2012January 22, 2021 by Nancy Atkinson

Astrophotos: A Colorful Moon

An unusual false color view of our Moon. Credit: César Cantú

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Recognize this? Yes, it is our own Moon, but using Photoshop, the photographer, César Cantú from the Chilidog Observatory in Monterrey, Mexico extracted the Moon’s colors and exaggerated them just a bit. “Although exaggerated, the color components are the real highlights,” César said, “with blue indicating a significant amount of titanium, and the orange areas with little iron or titanium. These colorful images are more easy to perform That thanks to digital cameras that detect colors — where with analog cameras, it is still impossible.”

César took the image on April 6, 2012. See his website for more details.

Want to get your astrophoto featured on Universe Today? Join our Flickr group, post in our Forum or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.

March 28, 2012December 23, 2015 by Jason Major

“Snowing Microbes” On Saturn’s Moon?

Cassini image of Enceladus from Dec. 2010 (NASA/JPL/SSI)

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Enceladus, Saturn’s 318-mile-wide moon that’s become famous for its ice-spraying southern jets, is on astronomers’ short list of places in our own solar system where extraterrestrial life could be hiding — and NASA’s Cassini spacecraft is in just the right place to try and sniff it out.

On March 27, Cassini came within 46 miles (74 km) of Enceladus’ south pole, the region where the moon’s many active water-ice jets originate from. This was Cassini’s closest pass yet over the southern pole, allowing the spacecraft to use its ion and neutral mass spectrometer — as well as its plasma spectrometer, recently returned to service — to taste the icy spray emanating from deep fissures called “tiger stripes” that scar Enceladus’ surface.

(Fly along with Cassini toward Enceladus’ jets here.)

“More than 90 jets of all sizes near Enceladus’s south pole are spraying water vapor, icy particles, and organic compounds all over the place,” said Carolyn Porco, planetary scientist and Cassini Imaging science team leader. “Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth’s oceans.”

In addition to water, salt and organics, there is also a surprising amount of heat — heat generated in part by tidal friction, helping keep Enceladus’ underground water reserves liquid.

“If you add up all the heat, 16 gigawatts of thermal energy are coming out of those cracks,” Porco said.

This creates, in effect, a so-called “Goldilocks zone” of potential habitability orbiting around Saturn… a zone that Cassini has easy access to.

“It’s erupting out into space where we can sample it. It sounds crazy but it could be snowing microbes on the surface of this little world,” Porco said. “In the end, it’s the most promising place I know of for an astrobiology search. We don’t even need to go scratching around on the surface. We can fly through the plume and sample it. Or we can land on the surface, look up and stick our tongues out. And voilà…we have what we came for.”

enceladus_stripe_11-30-10-1 — Cassini's view down into a jetting "tiger stripe" in August 2010

Cassini’s latest results — and images! — from the flyby should be landing on Earth any time now. Stay tuned to Universe Today for more updates on Cassini and Enceladus.