News / Science & Technology

'Man in the Moon' Explained

The Earth (unseen) casts a faint shadow over the southwestern part of a full moon during the penumbral lunar eclipse in Cairo October 19, 2013. A penumbral lunar eclipse occurs when the moon crosses the Earth's shadow, causing a slight dimming on the moon
The Earth (unseen) casts a faint shadow over the southwestern part of a full moon during the penumbral lunar eclipse in Cairo October 19, 2013. A penumbral lunar eclipse occurs when the moon crosses the Earth's shadow, causing a slight dimming on the moon

Related Articles

NASA Heads Back to the Moon

Unmanned rocket blasted off late Friday from Virginia's Eastern Shore with robotic explorer that will study lunar atmosphere, dust

NASA Breaks Data Transmission Speed Record With Laser Shot to Moon

NASA downloaded data at a rate of 622 megabits per second (Mbps) using a pulsed laser beam
VOA News
Scientists believe they know why the near side of the moon appears to have larger impact craters than the far side.

"Since time immemorial, humanity has looked up and wondered what made the man in the moon," said Maria Zuber, a geophyisics professor the Massachusetts Institute of Technology (MIT) and the principal investigator with NASA's Gravity Recovery and Interior Laboratory (GRAIL). "We know the dark splotches are large, lava-filled, impact basins that were created by asteroid impacts about four billion years ago. GRAIL data indicate that both the near side and the far side of the moon were bombarded by similarly large impactors, but they reacted to them much differently.”

Much of the bombardment of the moon occurred about 4 billion years ago, an era termed the Late Heavy Bombardment (LHB). During that time, a hailstorm of giant asteroids pummeled the solar system, slamming into the moon, along with young planets like Mercury, Venus, Earth, and Mars. Earth lacks most traces from this period because of erosion and plate tectonics.

Data from NASA’s twin GRAIL probes, which orbited the moon from January to December 2012. During its mission, the probes circled the moon, making measurements of its gravity. Scientists from MIT and the University of Paris used this data to generate a highly detailed map of the moon’s crust, showing areas where the crust thickens and thins. In general, the group observed that the moon’s near side has a thinner crust than its far side.

Katarina Miljkovic of the Institut de Physique du Globe de Paris, generated computer simulations of asteroid impacts on the moon by plugging in crustal thickness data from GRAIL. Milijkovic also incorporated estimates of the moon’s early internal temperatures from thermal modeling, based in part on lava deposits that flooded the large impact basins on the moon’s near side. Scientists have observed that more volcanic activity occurred on the near side, generating higher internal temperatures than on the moon’s far side.

“Impact simulations indicate that impacts into a hot, thin crust representative of the early moon’s near-side hemisphere would have produced basins with as much as twice the diameter as similar impacts into cooler crust, which is indicative of early conditions on the moon’s far-side hemisphere,” notes Miljkovic.

Together, the findings seem to indicate that the asteroids impacted the moon with less intensity than previously thought during the LHB. The asteroids also may have been smaller than previously thought.

Zuber said the near side’s thinner crust and higher temperatures may have made the surface more deformable than the thicker, cooler crust of the moon’s far side. These results suggest that the LHB may have involved less massive asteroids than scientists have thought.

“I’d certainly been a believer in the Late Heavy Bombardment from looking at those large impact basins,” Zuber said. “The idea of a Late Heavy Bombardment remains, but it will be have to be re-examined.”

Here's a short video about the study:

You May Like

Karzai's Legacy: Missed Opportunities?

Afghanistan's president leaves behind a much different nation than the one he inherited, yet his legacy from 13 years in power is getting mixed reviews More

US Urges Restraint in Hong Kong Protests

Protesters angered by Beijing's decision to only approve candidates that it sanctions for Hong Kong's leadership elections in 2017 More

Archive of Forgotten UCLA Speeches Offers Snapshot of History

Recordings of prominent voices in social change, politics, science and literature from 1960s, early 1970s now available on YouTube More

This forum has been closed.
Comment Sorting
Comments
     
by: Yoshi from: Sapporo
November 10, 2013 8:02 PM
Hi, Norimaki and Barrie, it is very kind of you to answer me. Now I understand centrifugal force working on the moon from the earth would explain the reasons of my qestions. Probably the core and magma once active are also lopsided to some extent toward the earth side. So, maybe the temperature is higher and volcanic activity is more active on the near side.

I am sorry but one more question comes up again. How come the moon rotates at the same period as its revorution?


by: Barrie Templeton from: Calgary, Alberta
November 10, 2013 9:24 AM
If I remember correctly, the moon is believed to have been ripped from the earth, and both rocks returned to spherical shapes due to centrifugal forces. If this theory is still valid, it might explain the thinner crust on the near side, and also may be the reason why it always puts the same face to the larger orb. If you have an out-of-balance ball, such as an old softball which has become lopsided, it will, when thrown, tend to put one side more toward the ground as it flies. This may be difficult to observe due to rather short travel times, but should be measurable with proper instruments such as slow-motion cameras. If the thinner-crust side is also the part that was attached to the planet prior to ejection, I believe the thinness is self-explanatory, as that area would have been hotter because of its proximity to the magma in the earth's core.


by: Norimaki Senbei from: Tokyo
November 09, 2013 6:31 PM
The moon is orbiting around the Earth without rotating on its axis, so outward force which is called "centrifugal force" works on only the far side. That's the cause of the difference of the thickness of the crust.


by: Yoshi from: Sapporo
November 08, 2013 8:10 PM
Thank you VOA for interesting stories every time. I did not know diameters of craters are different between the near side and far side. I understand how it might occur by your explanation.

After that, I would like to ask how come the crust is thinner and temperature is higher on the near side than the far side. In adission, how come volcanic activity was more on the near side?

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Treasure Hunters Seek 'Hidden Treasure' in Central Kenyai
X
Gabe Joselow
September 29, 2014 6:20 PM
Could a cave in a small village in central Kenya be the site of buried treasure? A rumor of riches, left behind by colonialists, has some residents dreaming of wealth, while others see it as a dangerous hoax. VOA's Gabe Joselow has the story.
Video

Video Treasure Hunters Seek 'Hidden Treasure' in Central Kenya

Could a cave in a small village in central Kenya be the site of buried treasure? A rumor of riches, left behind by colonialists, has some residents dreaming of wealth, while others see it as a dangerous hoax. VOA's Gabe Joselow has the story.
Video

Video Iran's Rouhani Skeptical on Syria Strikes

Iranian President Hassan Rouhani expressed skepticism Friday that U.S.-led airstrikes in Iraq and Syria could crush Islamic State militants. From New York, VOA’s Margaret Besheer reports the president was also hopeful that questions about Iran’s nuclear program could be resolved soon.
Video

Video US House Speaker: Congress Should Debate Authorization Against IS

As wave after wave of U.S. airstrikes target Islamic State militants, the speaker of the Republican-controlled House of Representatives says he would be willing to call Congress back into session to debate a formal, broad authorization for the use of military force. VOA’s Michael Bowman reports from Washington, where legislators left town 10 days ago for a seven-week recess.
Video

Video Ebola Patients Find No Treatment at Sierra Leone Holding Center

At a holding facility in Makeni, central Sierra Leone, dozens of sick people sit on the floor in an empty university building. They wait in filthy conditions. It's a 16-hour drive by ambulance to Kailahun Ebola treatment center. Adam Bailes was there and reports on what he says are some of the worst situations he has seen since the beginning of this Ebola outbreak. And he says it appears case numbers may already be far worse than authorities acknowledge.
Video

Video Identifying Bodies Found in Texas Border Region

Thousands of immigrants have died after crossing the border from Mexico into remote areas of the southwestern United States in recent years. Local officials in south Texas alone have found hundreds of unidentified bodies and buried them in mass graves in local cemeteries. Now an anthropologist and her students at Baylor University have been exhuming bodies and looking for clues to identify them. VOA’s Greg Flakus has more from Waco, Texas.
Video

Video Ebola Robs Liberians of Chance to Say Good-Bye to Loved Ones

In Liberia, where Ebola has killed more than 1,500 people, authorities have worked hard to convince people to allow specialized burial teams to take away dead bodies. But these safety measures, while necessary, make it hard for people to say good bye to their loved ones. VOA's Anne Look reports on the tragedy from Liberia.
Video

Video Reconstruction? What Reconstruction? Life After War in Gaza

It’s been a month since Israel and the Palestinians agreed to a ceasefire to end 52 days of an air and tank war that left 60,000 homes in Gaza damaged or destroyed and 110,000 homeless. Sharon Behn reports that lack of reconstruction is leading to despair.
Video

Video US, Saudi Arabia and UAE Hit Islamic State's Oil Revenue

The United States, Saudi Arabia and the United Arab Emirates have bombed oil facilities operated by Islamic State militants in Syria. It was a truly collaborative effort, with the two Arab countries dropping the majority of the bombs. The 12 refineries targeted were estimated to generate as much as $2 million per day for the terrorist group. VOA Pentagon correspondent Carla Babb has the story.
Video

Video Russia's Food Sanctions Raise Price Worries, Hopes for Domestic Production

Russia retaliated against Western sanctions imposed for its actions in Ukraine by halting food imports from the West. The temporary import ban on food from Australia, the European Union, Norway and North America has Russian consumers concerned that they could face a sharp increase in food prices. But in an ironic twist, the restrictions aimed at the Kremlin have made Russia's domestic food producers hopeful this can boost their business. VOA's Daniel Schearf reports from Moscow.
Video

Video Washington to Pyongyang: 'Shut This Evil System Down'

U.S. Secretary of State John Kerry is calling on North Korea to shut down prison camps and other human rights abuses following a United Nations Commission of Inquiry into "widespread and systematic human rights violations." VOA State Department Correspondent Scott Stearns reports from the United Nations.
Colonel Steve ‘Spiros’ Pisanos left Greece and came to the U.S. to learn to fly. He flew fighters for the Allies in World War II, narrowly escaping death multiple times.Colonel Steve ‘Spiros’ Pisanos left Greece and came to the U.S. to learn to fly. He flew fighters for the Allies in World War II, narrowly escaping death multiple times.

AppleAndroid