News / Science & Technology

    Scientists Think Earth Once Had 2 Moons

    Full Moon as seen from Apollo 11 (1969)
    Full Moon as seen from Apollo 11 (1969)
    Jessica Berman

    A new theory by planetary scientists says the Earth may once have been orbited by two moons, which formed early in the history of the solar system and collided slowly into one another to form a single Moon.  

    Collision course

    Scientists believe the Moon was formed when a Mars-sized object crashed into Earth some 4.5 billion years ago and the debris accreted, or came together to form the Moon.

    But to Erik Asphaug a planetary scientist at the University of California Santa Cruz, that does not address what astronomers call the lunar dichotomy between the visible side of the moon, marked by craters and a thin crust, and the far side of the moon, known to contain a thicker crust and mountain ranges topping 3,000 meters.

    Using a computer model, Asphaug and Martin Jutzi of the University of Bern in Switzerland devised a scenario of what might have caused the geographic dichotomy between the visible and far sides of the Moon.  They believe it was caused by a slow-moving collision, less than 2.5 kilometers per second, by a nearby smaller moon.

    “It turns out when the impact that is striking the moon comes from right next door to the moon, it doesn’t have a lot of velocity - it’s a pretty slow collision," said Asphaug. "And by the time it hits the moon, it doesn’t have enough energy to excavate a big crater.  All it has the velocity to do is squash itself flat as a big pancake.  And that was a real surprising finding of the result, and when we saw that in the renderings of the computer simulations, we knew we were on to something pretty interesting.”

    The theory

    How did this collision between the two moons occur?  Scientists believe the smaller sister moon, made of the same rocky debris as the larger moon became stuck in the gravity between Earth and the bigger moon billions of years ago, drawing the smaller lunar object into an impact with the moon.

    Paul Spudis, a planetary scientist at the Lunar and Planetary Institute in Houston, Texas is withholding judgment on the theory.  

    “It’s an intriguing idea and like all new ideas, we need to evaluate it carefully," said Spudis. "But I think there are some issues with it.  And I’m not against it and I’m not for it.  I prefer just to remain skeptical at the moment.”

    Scientists believe the lunar dichotomy could be explained if they could compare mineral samples from the near and far sides of the moon.

    The US space agency NASA will next month launch the GRAIL or Gravity Recovery and Interior Laboratory mission that should help increase astronomers’ understanding of the moon.  GRAIL’s twin spacecraft will fly in tandem orbits around the moon, measuring its gravity fields.

    It is hoped the mission, which will analyze the moon’s crust through to its core, will help scientists better understand the formation of rocky planets in our solar system.

    An article on the possibility of two moons in Earth’s orbit is published in the journal Nature.

    You May Like

    US Leaders Who Served in Vietnam War Look Back and Ahead

    In New York Times opinion piece, Secretary of State John Kerry, Senator John McCain and former Senator Bob Kerrey say as US strengthens relations with Vietnam, it is important to remember lessons learned from war

    Who Are US Allies in Fight Against Islamic State?

    There is little but opportunism keeping coalition together analysts warn — SDFs Arab militias are not united even among themselves, frequently squabble and don’t share Kurds' vision for post-Assad Syria

    Learning Foreign Language Helps US Soldiers Bridge Culture Gap

    Effective interaction with local populations part of everyday curriculum at Monterey, California, Defense Language Institute

    This forum has been closed.
    Comments
         
    There are no comments in this forum. Be first and add one

    Featured Videos

    Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
    Vietnamese-American Youth Optimistic About Obama's Visit to Vietnami
    X
    Elizabeth Lee
    May 22, 2016 6:04 AM
    U.S. President Barack Obama's visit to Vietnam later this month comes at a time when Vietnam is seeking stronger ties with the United States. Many Vietnamese Americans, especially the younger generation, are optimistic Obama’s trip will help further reconciliation between the two former foes. Elizabeth Lee has more from the community called "Little Saigon" located south of Los Angeles.
    Video

    Video Vietnamese-American Youth Optimistic About Obama's Visit to Vietnam

    U.S. President Barack Obama's visit to Vietnam later this month comes at a time when Vietnam is seeking stronger ties with the United States. Many Vietnamese Americans, especially the younger generation, are optimistic Obama’s trip will help further reconciliation between the two former foes. Elizabeth Lee has more from the community called "Little Saigon" located south of Los Angeles.
    Video

    Video First-generation, Afghan-American Student Sets Sights on Basketball Glory

    Their parents are immigrants to the United States. They are kids who live between two worlds -- their parents' homeland and the U.S. For many of them, they feel most "American" at school. It can be tricky balancing both worlds. In this report, produced by Beth Mendelson, Arash Arabasadi tells us about one Afghan-American student who seems to be coping -- one shot at a time.
    Video

    Video Newest US Citizens, Writing the Next Great Chapter

    While universities across the United States honor their newest graduates this Friday, many immigrants in downtown Manhattan are celebrating, too. One hundred of them, representing 31 countries across four continents, graduated as U.S. citizens, joining the ranks of 680,000 others every year in New York and cities around the country.
    Video

    Video Vietnam Sees Strong Economic Growth Despite Incomplete Reforms

    Vietnam has transformed its communist economy to become one of the world's fastest-growing nations. While the reforms are incomplete, multinational corporations see a profitable future in Vietnam and have made major investments -- as VOA's Jim Randle reports.
    Video

    Video Qatar Denies World Cup Corruption

    The head of Qatar’s organizing committee for the 2022 World Cup insists his country's bid to host the soccer tournament was completely clean, despite the corruption scandals that have rocked the sport’s governing body, FIFA. Hassan Al-Thawadi also said new laws would offer protection to migrants working on World Cup construction projects. VOA's Henry Ridgwell reports.
    Video

    Video Infrastructure Funding Puts Cambodia on Front Line of International Politics

    When leaders of the world’s seven most developed economies meet in Japan next week, demands for infrastructure investment world wide will be high on the agenda. Japanese Prime Minister Shinzo Abe’s push for “quality infrastructure investment” throughout Asia has been widely viewed as a counter to the rise of Chinese investment flooding into region.
    Video

    Video Democrats Fear Party Unity a Casualty in Clinton-Sanders Battle

    Democratic presidential front-runner Hillary Clinton claimed a narrow victory in Tuesday's Kentucky primary even as rival Bernie Sanders won in Oregon. Tensions between the two campaigns are rising, prompting fears that the party will have a difficult time unifying to face the presumptive Republican nominee, Donald Trump. VOA national correspondent Jim Malone has more from Washington.
    Video

    Video Portrait of a Transgender Marriage: Husband and Wife Navigate New Roles

    As controversy continues in North Carolina over the use of public bathrooms by transgender individuals, personal struggles with gender identity that were once secret are now coming to light. VOA’s Tina Trinh explored the ramifications for one couple as part of trans.formation, a series of stories on transgender issues.
    Video

    Video Amerikan Hero Flips Stereotype of Middle Eastern Character

    An Iranian American comedian is hoping to connect with American audiences through a film that inverts some of Hollywood's stereotypes about Middle Eastern characters. Sama Dizayee reports.
    Video

    Video Budding Young Inventors Tackle City's Problems with 3-D Printing

    Every city has problems, and local officials and politicians are often frustrated by their inability to solve them. But surprising solutions can come from unexpected places. Students in Baltimore. Maryland, took up the challenge to solve problems they identified in their city, and came up with projects and products to make a difference. VOA's June Soh has more on a digital fabrication competition primarily focused on 3-D design and printing. Carol Pearson narrates.

    Special Report

    Adrift The Invisible African Diaspora