The NASA illustration above provides a comparison for how big the moons of Mars appear to be, as seen from the surface of the red planet, in relation to the size that Earth’s moon appears to be when seen from the surface of Earth. Earth’s moon actually has a diameter more than 100 times greater than the larger Martian moon, Phobos. However, the Martian moons orbit much closer to their planet than the distance between Earth and Earth’s moon.
Deimos, at far left, and Phobos, beside it, are shown together as they actually were photographed by the mast camera on NASA’s Mars rover Curiosity on August 1. The images are oriented so that north is up.
A video clip assembled from the images can be viewed on YouTube.
Large craters on Phobos are clearly visible in these images from the surface of Mars. No previous images from missions on the surface caught one moon eclipsing the other, NASA said.
These observations of Phobos and Deimos help researchers make knowledge of the moons’ orbits even more precise.
“The ultimate goal is to improve orbit knowledge enough that we can improve the measurement of the tides Phobos raises on the Martian solid surface, giving knowledge of the Martian interior,” said Mark Lemmon of Texas A&M University. He is a co-investigator for use of Curiosity’s mast camera.
NASA’s Mars Science Laboratory project is using Curiosity and the rover’s 10 science instruments to investigate the environmental history within Gale Crater, a location where the project has found that conditions were long ago favorable for microbial life.