Moons of our Solar System
Moons of our Solar System

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

Moons of our Solar System

3.2 Phobos seen from the surface of Mars

According to John Murray, the answer is that the grooves were formed when Phobos passed through ejecta flung out from an impact on Mars – like a car passing through a hail of machine-gun bullets.

Phobos is only about 6000 km above the surface of Mars, and this is close enough to be within range of ejecta flung out from large impacts.

This video was shot from the surface of Mars by NASA’s Mars Curiosity Rover on 1 August 2013. It shows Phobos, the nearer to Mars of the two moons, passing in front of Deimos. Although Phobos is very much smaller than our Moon, its orbit is so low that in Mars’ sky it looks about half as wide as the Moon does in our own sky. The sequence has been speeded up from an actual elapsed time of 55 seconds.

Download this video clip.Video player: moons_1_vid033.mp4
Interactive feature not available in single page view (see it in standard view).

See also: Phobos grooves as tidal stretch marks? [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] An alternative explanation of Phobos’s grooves from the November 2015 annual Meeting of the Division of Planetary Sciences of the American Astronomical Society.

MOONS_BOC_1

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus