After many years of being shrouded in mystery, the reason behind the unusual appearance of Phobos, the largest moon of Mars, has now been brought to light.
Phobos typically resembles the planet-destroying Death Star in Star Wars because of the presence of a massive crater on the Martian moon's surface. Stickney crater, the mega crater on Phobos, now covers half the moon. The origin of the mega crater has eluded a convincing explanation until now.
The mystery was lifted after numerical simulations conducted by Lawrence Livermore National Laboratory gave new insights into the crater.
The new study, spearheaded by Jared Rovny, a summer student from Yale University, has LLNL planetary defense team members Megan Bruck Syal, Mike Owen and Paul Miller co-authors.
The Stickney Crater Mystery
In their study, the LLNL physicists demonstrate a scenario wherein an asteroid or comet hits Phobos and Stickney crater gets formed. The scenario asserts that the hard-hitting object did not destroy the Martian moon completely.
The study, which debunks all previous theories on the grooved terrain of Phobos, was published in Geophysical Research Letters and gives many convincing answers.
"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," says Syal.
The computational models raise many scenarios to account for the size and speed of the impactor. According to Syal, one possible scenario was that an object measuring 250 meters (820 feet) across made impact at a speed of 6 kilometers per second (3.73 miles per second).
Another scenario that may explain the Stickney crater formation is a 200-meter (656-foot) object impacting into Phobos at 8 kilometers per second (4.97 miles per second).
It may be recalled that past 2D simulations of lower resolutions were not successful in replicating the Stickney crater successfully as the new study has done.
Breaking Many Myths
According to the researchers, the weakness of earlier studies was that they failed to account for the porosity of Phobos' crust, which is significant because the moon is less dense compared to the surface of its mother planet.
The 3D simulations also disprove a previous assumption that the parallel grooves in the crater were also caused by the impact that created the Stickney crater. What the simulations suggest is that slow-rolling boulders triggered by the impact may have created the grooves. However, further study would be necessary to test whether this theory is plausible.
