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
TEXT SIZE - +
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

Multimedia Anti-Keystone XL Protests Continue

Demonstrators are worried about pipeline's effect on climate change, their traditional way of life, health and safety More

Thailand's Political Power Struggle Continues

Court gave Prime Minister Yingluck Shinawatra until May 2 to prepare her defense over abuse of power charges but uncertainty remains over election timing More

Malaysia Plane Search Tests Limits of Ocean Mapping Technology

Expert tells VOA existing equipment’s maximum operating depth is around 6 kilometers as operation continues on ocean bed for any trace of MH370 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.
Pet Kangaroo Helps Spread Environmental Messagei
X
Penelope Poulou
April 22, 2014 5:53 PM
Children’s author Julia Heckathorn travels the world to learn about different ecosystems and endangered animals. She pours her knowledge into children’s books, hoping the next generation will right the environmental wrongs of our times. As in many children's books, the main character in Heckathorn's stories is an animal. Unlike those other characters, though, this one is real - a kangaroo, that lives in the author’s backyard. VOA’s Penelope Poulou has more.
Video

Video Pet Kangaroo Helps Spread Environmental Message

Children’s author Julia Heckathorn travels the world to learn about different ecosystems and endangered animals. She pours her knowledge into children’s books, hoping the next generation will right the environmental wrongs of our times. As in many children's books, the main character in Heckathorn's stories is an animal. Unlike those other characters, though, this one is real - a kangaroo, that lives in the author’s backyard. VOA’s Penelope Poulou has more.
Video

Video Pro-Russian Separatists Plan 'Federalization Referendum' in Eastern Ukraine

Pro-Russian separatists in eastern Ukraine say they plan to move forward next month with a referendum vote for greater autonomy, despite the Geneva agreement reached with Russia, the U.S. and Ukraine to end the political conflict. VOA's Brian Padden reports from the city of Donetsk in Eastern Ukraine.
Video

Video Pope Francis Hopes Dual Canonizations Will Reconcile Church

On April 27, two popes - John the XXIII and John Paul II - will be made saints in a ceremony at St. Peter’s Square. VOA religion correspondent Jerome Socolovsky says the dual canonization is part of the current pope’s program to reconcile liberals and conservatives in the Roman Catholic Church.
Video

Video In Capturing Nature's Majesty, Film Makes Case for Its Survival

French filmmaker Luc Jacquet won worldwide acclaim for his 2005 Academy Award-winning documentary "March of the Penguins". Now Jacquet is back with a new film that takes movie-goers deep into the heart of a tropical rainforest - not only to celebrate its grandeur, but to make the case for its survival. VOA's Rosanne Skirble reports.
Video

Video Boston Marathon Bittersweet for Many Runners

Monday's running of the Boston Marathon was bittersweet for many of the 36,000 participants as they finished the run that was interrupted by a double bombing last year. Many gathered along the route paid respect to the four people killed as a result of two bombings near the finish line. VOA's Carolyn Presutti returned to Boston this year to follow two runners, forever changed because of the crimes.
Video

Video International Students Learn Film Production in World's Movie Capital

Hollywood - which is part of Los Angeles - is the movie capital of the world, and many aspiring filmmakers go there in hopes of breaking into the movie business. Mike O'Sullivan reports that regional universities are also a magnet for students who hope to become producers or directors.
Video

Video Pacific Rim Trade Deal Proves Elusive

With the U.S.-led war in Iraq ended and American military involvement in Afghanistan winding down, President Barack Obama has sought to pivot the country's foreign policy focus towards Asia. One aspect of that pivot is the negotiation of a free-trade agreement among 12 Pacific Rim nations. But as Obama leaves this week on a trip to four Asian countries he has found it very difficult to complete the trade pact. VOA's Ken Bredemeier has more from Washington.
Video

Video Autistic Adults Face Housing, Job Challenges

Many parents of children with disabilities fear for the future of their adult child. It can be difficult to find services to help adults with disabilities - physical, mental or emotional - find work or live on their own. The mother of an autistic boy set up a foundation to advocate for the estimated 1.2 million American adults with autism, a developmental disorder that causes communication difficulties and often social difficulties. VOA's Faiza Elmasry reports.
AppleAndroid