Nav: Home

How this Martian moon became the 'Death Star'

October 12, 2016

Mars' largest moon, Phobos, has captured public imagination and been shrouded in mystery for decades. But numerical simulations recently conducted at Lawrence Livermore National Laboratory (LLNL) have shed some light on the enigmatic satellite.

The dominant feature on the surface of Phobos (22-kilomters across) is Stickney crater (9-km across), a mega crater that spans nearly half the moon. The crater lends Phobos a physical resemblance to the planet-destroying Death Star in the film "Star Wars." But over the decades, understanding the formation of such a massive crater has proven elusive for researchers.

For the first time, physicists at LLNL have demonstrated how an asteroid or comet impact could have created Stickney crater without destroying Phobos completely. The research, which also debunks a theory regarding the moon's mysterious grooved terrain, was published in Geophysical Review Letters.

"We've demonstrated that you can create this crater without destroying the moon if you use the proper porosity and resolution in a 3D simulation," said Megan Bruck Syal, an author on the paper and member of the LLNL planetary defense team. "There aren't many places with the computational resources to accomplish the resolution study we conducted."

The study showed that there is a range of possible solutions for the size and speed of the impactor, but Syal says one possible scenario is an impact object 250 meters across traveling close to 6 kilometers per second (kps).

Previous studies used 2D simulations at lower resolutions, and they were ultimately unable to replicate Stickney crater successfully. Additionally, prior studies failed to account for the porosity of the Phobos' crust in their calculations, critical given that Phobos is less dense than the Martian surface.

While the simulations show how a massive impact could have created Stickney crater, they also appear to disprove a related theory. Some have theorized that the hundreds of parallel grooves that appear to radiate from the crater were caused by the impact. However, the simulations in this study show that fracture patterns in the crust of Phobos would be nothing like the straight, long, parallel grooves. On the other hand, the simulations do support the possibility of slow-rolling boulders mobilized by the impact causing the grooves. But more study would be required to fully test that theory.

The research served as a benchmarking exercise for the LLNL planetary defense team in their use of an open source code developed at LLNL called Spheral. The team uses codes like Spheral to simulate various methods of deflecting potentially hazardous Earth-bound asteroids.

"Something as big and fast as what caused the Stickney crater would have a devastating effect on Earth," Syal said. "If NASA sees a potentially hazardous asteroid coming our way, it will be essential to make sure we're able to deflect it. We'll only have one shot at it, and the consequences couldn't be higher. We do this type of benchmarking research to make sure our codes are right when they will be needed most."

The foundation this research is built upon is decades of investment in LLNL computational capabilities used to ensure the safety, security and effectiveness of the U.S. nuclear deterrent in the absence of nuclear testing - commonly known as stockpile stewardship. This research was also funded in part by the Laboratory Directed Research and Development Program at LLNL.

The study was spearheaded by Jared Rovny, a summer student visiting from Yale University. Other co-authors include LLNL computational physicist Mike Owen, who supported the research by mentoring Rovny and aligning the study to benchmark the Spheral code, and Paul Miller, who leads the planetary defense team at LLNL. Syal conducted followup modeling to confirm the findings and wrote the published paper. She will give a talk on the paper in Pasadena this month during the annual meeting of the American Astronomical Society's Division of Planetary Science.
-end-


DOE/Lawrence Livermore National Laboratory

Related Asteroid Articles:

Gigantic asteroid collision boosted biodiversity on Earth
An international study led by researchers from Lund University in Sweden has found that a collision in the asteroid belt 470 million years ago created drastic changes to life on Earth.
Uncovering the hidden history of a giant asteroid
A massive 'hit-and-run' collision profoundly impacted the evolutionary history of Vesta, the brightest asteroid visible from Earth.
Hubble watches spun-up asteroid coming apart
A small asteroid has been caught in the process of spinning so fast it's throwing off material, according to new data from NASA's Hubble Space Telescope and other observatories.
Hubble captures rare active asteroid
Thanks to an impressive collaboration bringing together data from ground-based telescopes, all-sky surveys and space-based facilities -- including the NASA/ESA Hubble Space Telescope -- a rare self-destructing asteroid called 6478 Gault has been observed.
Hayabusa2 probes asteroid for secrets
The first data received from the Hayabusa2 spacecraft in orbit of asteroid Ryugu helps space scientists explore conditions in the early solar system.
More Asteroid News and Asteroid Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Erasing The Stigma
Many of us either cope with mental illness or know someone who does. But we still have a hard time talking about it. This hour, TED speakers explore ways to push past — and even erase — the stigma. Guests include musician and comedian Jordan Raskopoulos, neuroscientist and psychiatrist Thomas Insel, psychiatrist Dixon Chibanda, anxiety and depression researcher Olivia Remes, and entrepreneur Sangu Delle.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...