European spacecraft captures rare movie of Martian moon Phobos
A rare movie of the Martian moon Phobos has been captured by the European Space Agency’s Mars Express spacecraft. The moon is set to be the target of an international mission to survey the Red Planet’s two natural satellites, and return a surface sample to Earth.
ESA's Mars Express probe has been exploring the Martian system for almost 16 years, and has captured a treasure trove of data on the Red Planet’s structure, makeup and climate, along with a host of other characteristics. Additionally, from time to time, the probe gets a closeup look at Mars’ two moons – Phobos and Deimos.
The new movie of Phobos was created from 41 individual images that were captured as the natural satellite passed roughly 2,400 km (1,491 miles) from the European spacecraft. Mars Express' High Resolution Stereo Camera captured the surface details of Phobos in exquisite detail, with a resolution of roughly 21 meters per pixel.
High-quality views of Phobos provide a rare opportunity for scientists to analyze the properties the lonely Martian moon, and could even be useful in planning future robotic missions hoping to probe its secrets.
One such endeavor – the Martian Moons eXploration (MMX) mission - is set to launch in 2024, and will visit both Phobos and Deimos in an attempt to determine the origins of both natural satellites. The ambitious mission will see MMX touch down on the surface of Phobos and retrieve a surface sample to be returned to Earth by 2029.
The new movie shows Phobos slowly rotating over 41 frames, as its apparent brightness increases and subsequently dims towards the end. The change in luminosity is the result of the alignment of the spacecraft relative to Phobos and the Sun. At the beginning of the video, Mars Express is imaging the natural satellite at an angle of 17º relative to the point at which light from the Sun was directly striking the moon. This is known as the "phase angle."
At its brightest point, the phase angle gets down to 0.02° before shifting to 15° by the end of the video.
It is rare for Mars Express to have a phase angle relative to Phobos of less than 1°. This kind of alignment occurs at most three times a year, with the next being in April, and then September next year.
Scroll down to watch the short movie, courtesy of ESA.