Hello,

We noticed you're browsing in private or incognito mode.

To continue reading this article, please exit incognito mode or log in.

Not a subscriber? Subscribe now for unlimited access to online articles.

The Moon’s Bumpy Gravity

Simulations based on lunar satellite data explain gravitational anomalies.

Ever since the first satellites were sent to the moon to scout landing sites for Apollo astronauts, scientists have noticed a peculiar phenomenon: as these probes orbited the moon, passing over certain craters and impact basins, they periodically veered off course, plummeting toward the lunar surface before pulling back up.

moon map
Red and blue represent stronger gravity gradients in this moon map based on data from NASA’s GRAIL mission.

As it turns out, the cause of such bumpy orbits was the moon itself. Over the years, scientists have observed that its gravity is stronger in some regions than others, creating a “lumpy” gravitational field. In particular, a handful of impact basins exhibit an unexpectedly strong gravitational pull. Scientists, who suspect that the explanation has to do with an excess distribution of mass below the lunar surface, have dubbed these regions mass concentrations, or “mascons.”

September/October MIT News cover
This story is part of the September/October 2013 Issue of the MIT News magazine
See the rest of the issue
Subscribe

Exactly how these mascons came to be has remained a mystery—until now.

Using high-resolution gravity data from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission, researchers at MIT and Purdue University mapped the structure of several mascons and found that their gravitational fields resemble a bull’s-eye pattern: a center of strong gravity surrounded by alternating rings of weak and strong gravity.

To figure out what caused this gravitational pattern, the team created a computer model of lunar impacts and ran the model forward to simulate geological repercussions in the moon’s crust and mantle over both the short and long term. They found that the simulations reproduced the bull’s-eye pattern under just one scenario.

When an asteroid crashes into the moon, it sends material flying out, creating a dense band of debris around the crater’s perimeter. The impact sends a shock wave through the moon’s interior, reverberating within the crust and producing a counterwave that draws dense material from the lunar mantle toward the surface, creating a dense center within the crater. After hundreds of millions of years, the surface cools and relaxes, creating a bull’s-eye that matches today’s gravitational pattern.

This tumultuous chain of events was probably what led to today’s lunar mascons, says Maria Zuber, a professor of geophysics in the Department of Earth, Atmospheric and Planetary Sciences. The team’s results were published in Science.

“For the first time, we have a holistic understanding of the process that forms mascons,” says Zuber, who is also GRAIL’s principal investigator and MIT’s vice president for research. “There will be more details that emerge for sure, but the quality of the GRAIL data enabled rapid progress on this long-standing question.”

The race is on to define the new blockchain era. Get a leg up at Business of Blockchain 2019.

Register now
Next in MIT News
Want more award-winning journalism? Subscribe to MIT Technology Review.
  • Print + All Access Digital {! insider.prices.print_digital !}* Best Value

    {! insider.display.menuOptionsLabel !}

    The best of MIT Technology Review in print and online, plus unlimited access to our online archive, an ad-free web experience, discounts to MIT Technology Review events, and The Download delivered to your email in-box each weekday.

    See details+

    12-month subscription

    Unlimited access to all our daily online news and feature stories

    6 bi-monthly issues of print + digital magazine

    10% discount to MIT Technology Review events

    Access to entire PDF magazine archive dating back to 1899

    Ad-free website experience

    The Download: newsletter delivered daily

  • All Access Digital {! insider.prices.digital !}*

    {! insider.display.menuOptionsLabel !}

    The digital magazine, plus unlimited site access, our online archive, and The Download delivered to your email in-box each weekday.

    See details+

    12-month subscription

    Unlimited access to all our daily online news and feature stories

    Digital magazine (6 bi-monthly issues)

    Access to entire PDF magazine archive dating back to 1899

    The Download: newsletter delivered daily

  • Print Subscription {! insider.prices.print_only !}*

    {! insider.display.menuOptionsLabel !}

    Six print issues per year plus The Download delivered to your email in-box each weekday.

    See details+

    12-month subscription

    Print magazine (6 bi-monthly issues)

    The Download: newsletter delivered daily

/3
You've read of three free articles this month. for unlimited online access. You've read of three free articles this month. for unlimited online access. This is your last free article this month. for unlimited online access. You've read all your free articles this month. for unlimited online access. You've read of three free articles this month. for more, or for unlimited online access. for two more free articles, or for unlimited online access.

MIT News = for alumni only.

Are you an MIT alum?
Sign in now to read all MIT alumni news and class notes— or to manage your magazine subscription.

Sign in and read on