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Mars rover spots mini-moon's transit

NASA / JPL-Caltech / MSSS

A filtered photo from the Curiosity rover's Mastcam imaging system shows the transit of Deimos across the sun, as seen from Mars on Sept. 17.

NASA's Curiosity rover has sent back more snapshots of Martian mini-eclipses, the pyramid-shaped rock it's studying up close, and its own star-spangled hardware.

The first pictures from Curiosity's eclipse-watching sessions were received last weekend, focusing on Phobos, the larger of the Red Planet's two moons. That picture showed the satellite taking a slight bite from the sun's edge. Now we have images showing the smaller moon, Deimos, passing across the sun's disk on Sept. 17 (also known as Sol 42 of Curiosity's mission). Take a look at this animated GIF image from the good folks at UnmannedSpaceflight.com, and compare it with these videos from June's transit of Venus. Weirdly similar, right?

There's another shot of a Phobos transit, taken on the morning of Sol 42 on Mars. The Red Planet's moons never completely cover up the sun's disk, but the Sol 42 transit darkened more of the sun than the earlier Phobos mini-eclipse did.

Detailed analysis of these transit pictures will help the Curiosity team get a better sense of the interior structure of Mars and its moons, as Texas A&M's Mark Lemmon explained a couple of days ago. Phobos and Deimos aren't all that different in width (14 miles vs. 8 miles, respectively), but Phobos' apparent size as seen from the Martian surface is noticeably bigger because it orbits so much closer (5,800 miles vs. 14,580 miles for Deimos).

Now Curiosity is turning its attention to a rock that's been nicknamed "Jake Matijevic," in honor of an engineer at NASA's Jet Propulsion Laboratory who recently passed away. The rover has sent back fresh pictures of the rock, plus views of its U.S. flag medallion and the traditional presidential plaque:

Two images of the top half of the rock known as Jake Matijevic, captured by Curiosity's Mastcam imaging system, are shuffled in this video to produce a 3-D illusion.

NASA / JPL-Caltech

The shadow of Curiosity's robotic arm can be seen extending toward Jake in this view from the rover's navigation camera system.

NASA / JPL-Caltech / MSSS

This view of the American flag medallion on NASA's Curiosity rover was taken by the rover's Mars Hand Lens Imager on Sept. 19 (Sol 44). The flag is one of four "mobility logos" placed on the rover's mobility rocker arms. The circular medallion of the flag is made of anodized aluminum and measures 2.68 inches (68 millimeters) in diameter. The medallion was affixed with bolts to locations on the rocker arms where flight hardware was once considered, but ultimately deemed unnecessary. The other three medallions on the rover's rocker arms display the NASA logo, the Jet Propulsion Laboratory's logo and the Curiosity mission logo.

NASA / JPL-Caltech / MSSS

This view of Curiosity's deck shows a plaque bearing several signatures of US officials, including that of President Obama and Vice President Biden. The image was taken by the rover's Mars Hand Lens Imager on Sept. 19 (Sol 44). The plaque is located on the front left side of the rover's deck. The rectangular plaque is made of anodized aluminum and measures 3.94 inches (100 millimeters) tall by 3.23 inches (82 millimeters) wide. Similar plaques with signatures - including those of the sitting president and vice president - adorn the lander platforms for NASA's Spirit rover and Opportunity rover, which landed on Mars in January 2004

Where in the Cosmos
Curiosity's view of the transit of Deimos served as this week's "Where in the Cosmos" puzzle picture on the Cosmic Log Facebook page. There were lots of interesting guesses as to the nature of the black spot (Venus? Earth? Mercury? Planet X?), but Robert Dryden was the first to identify it correctly as Deimos. To reward his sharp eye for mini-eclipses, I'm sending him a complimentary pair of cardboard 3-D glasses, provided by Microsoft Research's WorldWide Telescope project. Those red-blue specs will come in handy for checking out Curiosity stereo views like this one, and this one, and this one. You can also feast your eyes on the 3-D views of the shuttle Endeavour produced by the Planetary Society's Emily Lakdawalla.

Want to be in on next Friday's puzzle? All you have to do is "like" the Cosmic Log Facebook page.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.