Millions of Earthlings were in a position to watch the full moon go dark during last Wednesday’s total lunar eclipse — and so was NASA’s Messenger probe, which is orbiting the planet Mercury, 66 million miles (107 million kilometers) away. Now you can get a Mercury's-eye view of the eclipse as well.
Mercury and Messenger are currently on the other side of the sun, off to the side from Earth's perspective. That was a perfect spot for seeing the sunlit moon blink out as it passed into Earth's shadow.
"From Mercury, the Earth and moon normally appear as if they were two very bright stars," Hari Nair, a planetary scientist at Johns Hopkins University Applied Physics Laboratory, said in a news release issued Friday. Earth is just five pixels across in the field of view for Messenger's narrow-angle camera, and the moon is just over one pixel across.
Messenger's science team produced a time-lapse video from 31 images of Earth and the moon, taken at two-minute intervals. Those pictures span the hour from 5:18 to 6:18 a.m. ET Oct. 8 — a time period during which the full moon's disk gradually became fully covered by the darkest part of Earth's shadow.
To enhance the eclipse effect, Nair said the images were enlarged to double the apparent size of the Earth-moon system, and the moon's brightness was increased by a factor of about 25.
This isn't the first time Messenger has gotten in on an interplanetary phenomenon. A year ago, the Mercury probe snapped a portrait of Earth and the moon at the same time that NASA's Cassini probe was taking a picture of Earth as seen from Saturn.
Seeing pictures of celestial bodies together, from different far-flung perspectives, helps us realize that we're all in one big solar system — and that today's robotic explorers are expanding our view of the planetary neighborhood.
Earth and Mars together
Another example of that wider perspective comes from NASA's Lunar Reconnaissance Orbiter. That spacecraft's narrow-angle camera snapped a full-disk, black-and-white picture of Earth — with a teeny-tiny Mars photobombing the scene.
Mars was about 70 million miles (112.5 million kilometers) away when the image was acquired on May 24, and Earth was about 234,062 miles (376,687 kilometers) away.
Arizona State University's Julie Stopar said the Lunar Reconnaissance Orbiter team made practice images of Mars for weeks to fine-tune the timing and the camera settings for the two-planet picture.
"The juxtaposition of Earth and Mars seen from the moon is a poignant reminder that the moon would make a convenient waypoint for explorers bound for the fourth planet and beyond," she wrote in an Oct. 2 posting to the website for the team behind the Lunar Reconnaissance Orbiter Camera, or LROC.
Volcanism on the moon
And here's the latest news from the LROC team: A study published in Nature Geoscience suggests there was volcanic activity on the moon less than 100 million years ago — and perhaps less than 50 million years ago.
The evidence comes from about 70 topographic anomalies, informally called "irregular mare patches," that have been linked to relatively recent basaltic eruptions.
"This finding is the kind of science that is literally going to make geologists rewrite the textbooks about the moon,” John Keller, LRO project scientist at NASA’s Goddard Space Flight Center, said in a NASA news release.
The authors of the Nature Geoscience paper, "Evidence for Basaltic Volcanism on the Moon Within the Past 100 Million Years," include Stopar as well as Sarah Braden, Mark Robinson, Samuel Lawrence, Carolyn van der Bogert and Harald Hiesinger.