Dang! NASA’s Curiosity rover beat me to it by just one day, spotting the asteroids Ceres and Vesta from the surface of Mars on Sunday April 20. Me? I caught them later that night from a comfortable location on Earth with a pair of 8×40 binoculars.
The rover aimed its high-resolution mast camera skyward to take the first-ever photos of the largest (Ceres) and brightest (Vesta) asteroids. Both objects are destinations of NASA’s Dawn Mission as we learned in this recent blog. The photo shows trailed images of both – it was a 12-second time exposure – and Mars’ smaller moon Deimos. The others were added to make a composite. While it looks like it was taken with a mobile phone, it’s one of very few photos taken of the night sky from another planet.
The two asteroids and three stars would be visible to someone of normal eyesight standing on Mars. Specks are effects of cosmic rays striking the camera’s light detector. Given that Mars is located closer to the asteroid belt than Earth, I checked the brightness of Ceres and Vesta. Interestingly, both are located in the constellation Virgo just as they are from our own planet right now, but their brightnesses differ. Vesta shines at magnitude +4 (+5.8 from Earth), making it a relatively easy naked eye object from the Martian ‘countryside’. Ceres is currently magnitude +7 from home but magnitude +5.8 and dimly visible with the naked eye from Mars.
Thinking about it a minute, it shouldn’t surprise us that both asteroids are traveling together in the same constellation as seen from both planets. Can you guess why? Remember that Mars was at opposition earlier this month and lined up with Earth on the same side of the sun. That alignment means that we both look out at virtually the same “springtime” constellations in our respective night skies AND look in nearly the same direction when viewing Ceres and Vesta. If Mars was on the opposite side of the sun, Martians would have to look in the opposite direction of the sky to see them.
“This imaging was part of an experiment checking the opacity of the atmosphere at night in Curiosity’s location on Mars, where water-ice clouds and hazes develop during this season,” said camera team member Mark Lemmon of Texas A&M University, College Station. “The two Martian moons were the main targets that night, but we chose a time when one of the moons was near Ceres and Vesta in the sky.”
We love it and wouldn’t complain if you guys shot more nighttime stuff. How about a sequence of images of the rising Earth or a longer time exposure showing star trails with the landscape faintly illuminated by the light of Phobos and Deimos?