In an exciting first, a new series of images taken by NASA's Mars rover Curiosity tracks the slow, steady passage of Mars's larger moon, Phobos, passing in front of its pint-sized little brother Deimos.
The observation of the two moons is key in creating an even more precise map of the moons' orbits.
"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. "We may also get data good enough to detect density variations within Phobos and to determine if Deimos' orbit is systematically changing."
However, while much may remain a mystery in regard to the two moons, researchers do know that the orbit of Phobos is slowly moving closer to Mars. Deimos's orbit, on the other hand, may be slowly moving away.
Lemmon, a co-investigator for use of Curiosity's Mast Camera (Mastcam), determined the moons would be visible crossing paths during a time shortly after Curiosity would already be awake transmitting data to NASA's Mars Reconnaissance Orbiter for relay to Earth, making the observations possible with little impact on the rover's energy budget.
Despite having a diameter less than one percent of Earth's moon, Phobos orbits much closer to Mars than Earth's moon does to it. As a result, Phobos appears roughly half as wide in the sky when viewed from Mars as Earth's moon does from Earth.
The most prominent feature on Phobos is the 6-mile crater known as Stickney, which, according to observations made by the Mars Global Surveyor, appears to be filled with fine dust.
Temperature measurements of the day and night sides of Phobos reveal variations so extreme that while one compares to something of a pleasant winter day in Chicago, just a few miles away is a climate harsher than an Antarctic night.