mars sees mercury transit
June 11, 2014

Mercury Transit Seen From Mars

Brett Smith for - Your Universe Online

Observers on Earth have tracked Venus and Mercury crossing the face of the Sun countless times, but the phenomenon has never been observed from another planet – until now.

On Tuesday, NASA announced that its Curiosity Rover had captured the first-ever observations of Mercury moving across the face of the Sun – also called a planetary transit – using its two-eyed Mast Camera (MastCam).

"This is a nod to the relevance of planetary transits to the history of astronomy on Earth," said Mark Lemmon, a MastCam team member from Texas A&M University, in a statement. "Observations of Venus transits were used to measure the size of the solar system, and Mercury transits were used to measure the size of the sun."

[ Watch the Video: Mercury In Front Of the Sun, Seen From Mars ]

The first imaging of Mercury from Mars, the closest planet to the Sun, covers only about one-sixth of one pixel as seen in the MastCam images. The result is the appearance of a shapeless darkening passing across the Sun. The darkening does trace Mercury's expected path based on orbital models.

The observations were actually recorded one week earlier – on June 3, 2014. Captured from the rover’s location inside Mars’ Gale Crater, the images also depict two sunspots about the size of Earth. The spots were seen moving at a slower pace than Mercury.

Mars is actually considered a much better vantage point for seeing planetary transits compared to Earth. Observers on Earth saw a Venus transit in June 2012, the last that can be seen from Earth this century. The next Mercury transit that can be seen from Earth will be May 9, 2016. The transits visible from Mars will be Mercury in April 2015, Venus in August 2030 and Earth in November 2084.

Before observing the Mercury transit, Curiosity completed an analysis of a sandstone sample collected on Mars last month. Portions of powdered rock collected by drilling into sandstone were examined for texture and composition using the camera and spectrometer at the end of Curiosity’s robotic arm.

"The drill tailings from this rock are darker-toned and less red than we saw at the two previous drill sites," said Jim Bell, the principal investigator for Mastcam from Arizona State University. "This suggests that the detailed chemical and mineral analysis that will be coming from Curiosity's other instruments could reveal different materials than we've seen before. We can't wait to find out!"

After drilling and analyzing the sample, the rover made preparations for continuing toward its long-term objective – Mount Sharp, the layered mountain at the middle of Mars’ Gale Crater. The rover is carrying with it some of the powdered sample material that can be delivered for further internal laboratory analysis during pauses in the trip.

The mission’s two prior rock-drilling locations, at mudstone targets, produced evidence last year of an ancient lakebed ecosystem with essential chemical elements and a chemical energy source that would have provided conditions favorable for microbial life.

Built by NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, the rover’s primary goal is to assess ancient habitable environments and major changes in Martian environmental conditions.