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

    Native Americans Ask: What About Our Water Supply?

    They say they have been facing a dangerous water contaminant for decades - uranium – but the problem has received far less attention than water contamination by lead in Flint, Michigan

    Pakistan's President Urges Nation Not to Celebrate Valentine's Day

    Mamnoon Hussain criticizes Valentine's Day, which falls on Sunday this year, as a Western import that threatens to undermine the Islamic values of Pakistan

    Mother of IS Supporter: Son Was Peaceful, 'Role Model'

    Somali-American Abdirizak Mohamed Warsame pleaded guilty Thursday to charges of conspiring to provide material support to Islamic State militants

    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.
    Two-thirds of World Faces Water Shortagei
    X
    February 12, 2016 7:31 PM
    Four billion people — or two out of every three on the planet — do not have enough water to meet their basic needs. That is far greater than previously thought, according to a new study that presents a more accurate picture of the problem. As VOA's Rosanne Skirble reports, the findings will help policymakers and the public craft solutions to address the threat.
    Video

    Video Two-thirds of World Faces Water Shortage

    Four billion people — or two out of every three on the planet — do not have enough water to meet their basic needs. That is far greater than previously thought, according to a new study that presents a more accurate picture of the problem. As VOA's Rosanne Skirble reports, the findings will help policymakers and the public craft solutions to address the threat.
    Video

    Video Gateway to Mecca: Historical Old Jeddah

    Local leader Sami Nawar's family has been in the Old City of Jeddah for hundreds of years and takes us on a tour of this ancient route to Mecca, also believed to be the final resting place of Adam's wife, Eve.
    Video

    Video New Technology Aims to Bring Election Transparency to Uganda

    A team of recent graduates from Uganda’s Makerere University has created a mobile application designed to help monitor elections and expose possible rigging. The developers say the app, called E-Poll, will make Uganda's democratic process fairer. From Kampala, VOA's Serginho Roosblad reports.
    Video

    Video As Refugees Perish, Greek Graveyards Fill

    Aid workers on the Greek island of Lesbos say they are struggling to bury the increasing number of bodies of refugees that have been recovered or washed up ashore in recent months.  The graveyards are all full, they say, yet as tens of thousands of people clamor to get out of Syria, it is clear refugees will still be coming in record numbers. For VOA, Hamada Elrasam reports from Lesbos, Greece.
    Video

    Video Russia Bristles at NATO Expansion in E. Europe

    Russian Foreign Minister Sergei Lavrov is meeting Friday with the head of NATO after the Western military alliance and the United States announced plans for the biggest military build-up in Europe since the Cold War. Russia has called NATO's moves a threat to stability in Europe. But NATO says the troop rotations and equipment are aimed at reassuring allies concerned about Russia as VOA's Daniel Schearf reports from Moscow.
    Video

    Video To Fight Zika, Scientists Target Mosquitoes

    Mosquitoes strike again. The Zika virus outbreak is just the latest headline-grabbing epidemic carried by these biting pests, but researchers are fighting back with new ways to control them. VOA's Steve Baragona takes a look.
    Video

    Video Mosul Refugees Talk About Life Under IS

    A top U.S. intelligence official told Congress this week that a planned Iraqi-led operation to re-take the city of Mosul from Islamic State militants is unlikely to take place this year. IS took over the city in June 2014, and for the past year and a half, Mosul residents have been held captive under its rule. VOA's Zana Omar talked to some families who managed to escape. Bronwyn Benito narrates his report.
    Video

    Video Scientists Make Progress Toward Better Diabetes Treatment, Cure

    Scientists at two of the top U.S. universities say they have made significant advances in their quest to find a more efficient treatment for diabetes and eventually a cure. According to the International Diabetes Federation, the disease affects more than 370 million people worldwide. VOA’s George Putic reports.
    Video

    Video NATO to Target Migrant Smugglers

    NATO has announced plans to send warships to the Aegean Sea to target migrant smugglers in the alliance's most direct intervention so far since a wave of people began trying to reach European shores.
    Video

    Video Russia's Catholics, Orthodox Hopeful on Historic Pope-Patriarch Meeting

    Russia's Catholic minority has welcomed an historic first meeting Friday in Cuba between the Pope and the Patriarch of Russia's dominant Orthodox Church. The Orthodox Church split with Rome in 1054 and analysts say politics, both church and state, have been driving the relationship in the centuries since. VOA's Daniel Schearf reports from Moscow.
    Video

    Video Used Books Get a New Life on the Streets of Lagos

    Used booksellers are importing books from abroad and selling them on the streets of Africa's largest city. What‘s popular with readers may surprise you. Chris Stein reports from Lagos.
    Video

    Video After NH Primaries All Eyes on South Carolina

    After Tuesday's primary in New Hampshire, US presidential candidates swiftly turned to the next election coming up in South Carolina. The so-called “first-in-the-South” poll may help further narrow down the field of candidates. Zlatica Hoke reports.
    Video

    Video Smartphone Helps Grow Vegetables

    One day, you may be using your smartphone to grow your vegetables. A Taipei-based company has developed a farm cube — a small, enclosed ecosystem designed to grow plants indoors. The environment inside is automatically adjusted by the cube, but it can also be controlled through an app. VOA's Deborah Block has more on the gardening system.
    Video

    Video Exhibit Turns da Vinci’s Drawings Into Real Objects

    In addition to being a successful artist, Renaissance genius Leonardo da Vinci designed many practical machines, some of which are still in use today, although in different forms. But a number of his projects were never realized — until today. VOA’s George Putic reports.