The NASA Curiosity rover has just seen the transits of both Martian moons across the face of the Sun, including one that occurred after the Sun had set.
In Andy Weir's book The Martian, the beached astronaut Mark Watney uses the times of rising and configuration of the Martian moons, Phobos and Deimos, as an approximate form of "account estimation" to help him find his way. Last week, an astute observer who scrutinized recent images of Curiosity's robot showed an equally interesting image: the shadow of the most intimate moon, Phobos, as it glided silently over the face of the Sun, after the Sun had set.
Just a few days before, Curiosity had also captured a transit of Deimos, and now NASA has published a set of images of both solar transits seen from the perspective of the mobile, using solar filters connected to the Curiosity Mastcam.
"More observations over time help pinpoint the details of each orbit," says Mark Lemmon (Institute of Space Sciences / Texas A & M University) in a recent press release. "Those orbits change all the time in response to the gravitational pull of Mars, Jupiter or even each Martian moon that pulls on the other."
Curiosity has seen such transits before, but this is the first time he sees the shadow of Phobos cross the sky after the Martian sunset.
Chasing the shadows of the moon on Mars
This unique phenomenon was noticed for the first time and was published by user FredK at the Unmanned Space Flight Forum on March 26. The images, taken by Navcam, to the right of Curiosity, seemed to show a shadow across the sky, probably projected through a thin layer of dust suspended in the faint Martian atmosphere.
This aroused the interest of Jet Propulsion Laboratory & # 39; s. Doug Ellison, which processed and stacked some of the images and then posted the thread on Twitter (he is @ doug_ellison). NASA later released a formal sequence of the incredible vision:
"We knew it was coming (we planned the observation to capture it after all)," says Ellison, "but it was amazing to see someone who discovered it … it was quite subtle in the raw audience .jpgs!"
Now, curiosity is not alien to the irregular transits of Phobos. (WWe refer to them as transits instead of eclipses, because the Moon has an average of 12 arc minutes and never fully covers the Sun of 20.5 arc minutes, as seen from the Martian surface. NASA engineers have even used observations of such events to determine by the precise orbits for the moon The opportunity has also broken transits of small Deimos in the past.
What is unique this time is that the final sequence catches the event. after local sunset. Ellison ran the circumstances for the rover by around 4:49 am Universal Time (UT) on March 26. And confirmed the transit. Heck, the shadow even glances disturbingly like a redux of the shadow of the Moon seen crossing the sky during a total solar eclipse on Earth.
Phobos and its shadow have also appeared in other images: NASA's Mars Global Surveyor orbiter has seen how the deformed shadow of the moon flits through the Martian landscape.
And Mars Insight has also recently documented a clear dimming when Phobos transited the midday sun as seen from the location of the lander:
Even insight is expected to detect small terrestrial tides raised by Phobos when it pbades overhead.
Phobos orbits Mars once every 7 hours and 39 minutes from only 3,721 miles (5,989 kilometers) above the Martian surface, as close as any moon orbits its host planet in the solar system. Because it orbits faster than the planet rotates, a Mars-based observer will see Phobos rise in the West and located in the east – a truly strange vision.
The post-sunset transit is a testament to what enthusiastic observers can present in planetary images, with a little bit of skill and patience. Maybe one day human eyes will witness the subtle shadow of Phobos gliding over it. Our best bet, however, is to travel to the slopes of Elysium Mons, where on November 10, 2084, one could spy on Phobos, Earth and the Moon to cross the Sun at the same time.
Of course, there is a bit of uncertainty in the calculation of such an distant event; we promise to run the simulation again in 2083. Let's see, by then I'll be there. . .