THIS IS HOW MARS’S BIGGEST MOON
CAME TO LOOK LIKE THE DEATH STAR
Thanks to an enormous ding on its surface known
as the Stickney Crater, Mars’s moon Phobos is said
to look like the Death Star from the Star Wars
movies. The crater is presumed to have been
caused by comet impact, but exactly how
a 9km-wide crater could have formed on
a 22km-wide moon without destroying it has
remained something of a mystery.
Now researchers at Lawrence Livermore
National Laboratory think they have the answer.
Using computer simulations, they found that
the most likely culprit was a comet with a 250m
diameter, travelling at close to six kilometers
per second.
Previous studies using 2D simulations lacked
the resolution to model the Stickney Crater
successfully and failed to account for the fact that
Phobos is made of much less dense material than
its host planet.
“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 researcher Megan Bruck Syal.
“There aren’t many places with the computational
resources to accomplish the resolution study
we conducted.”
As well as solving a longstanding mystery, this
research also acts as a proof of concept exercise for
the team’s modelling software, Spheral, which
they use 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 conse-
quences couldn’t be higher. We do this type
of benchmarking research to make sure our
codes are right when they will be needed most.”IN NUMBERS81,000
YEARS
The time it takes asteroid
impacts to completely
change the surface of the
Moon, according to
a seven-year study carried
out at Arizona State
University.122
The age of Jeanne Calment
when she died in 1997,
making her the oldest person
to ever live on official record.
Results from a global study
from the Albert Einstein
College of Medicine, New
York, suggest this may be
near to the maximum age
a human can ever reach.2
TRILLION
The number of galaxies in
the observable Universe, as
estimated using data taken
from the Hubble Space
Telescope. The figure was
previously thought to be
10 times smaller.SPACE
Was a comet responsible
for the formation of the
Stickney Crater, seen here
on the right of Phobos?