Space Friday: A Moon for Makemake, a Comet without a Tail, and Exomoons

Focusing Images of the Martian Surface and Curiosity Update

A new technique called Super-Resolution Restoration (SRR) developed at University College London (UCL) was recently used to focus in on specific objects on Mars’s surface in greater detail. A paper describing the technique was published in Planetary and Space Science in February, although it has only been implemented in the last couple months.

SSR requires multiple images (often four to eight) of the same place, but from different angles, which are then matched, overlapped, and stacked. Using pictures fairly recently taken by the MRO’s HiRISE camera, researchers we able to focus and refine images that originally had a resolution of 25 centimeters (10 inches) per pixel to a much more detailed five centimeters (two inches). So far, more resolved images of the previously lost British Beagle-2 lander, the ancient lakebeds found by NASA’s Curiosity rover, tracks from NASA’s Spirit (MER-A) rover, and the Home Plate rocks have been released.

The nature of Mars’s thin atmosphere and slowly changing geology allows the team to use high resolution images taken of the same location from over the past ten years. This same technique would not be useful here on Earth where our turbulent, continuously changing atmosphere would require the images used for comparison to all have been taken within a few seconds of each other.

Co-author Jan-Peter Muller, elaborates on the ramifications of the technique: “We now have the equivalent of drone-eye vision anywhere on the surface of Mars where there are enough clear repeat pictures. It allows us to see objects in much sharper focus from orbit than ever before and the picture quality is comparable to that obtained from landers. As more pictures are collected, we will see increasing evidence of the kind we have only seen from the three successful rover missions to date. This will be a game-changer.”

Speaking of rovers currently taking images on the Martian surface, Curiosity is set to clear its 0.4-kilometer (quarter-mile) trek across the Naukluft Plateau, the “most rugged and difficult-to-navigate terrain” it has yet encountered on its journey up Mount Sharp. Fortunately, it looks like the rough path did not accelerate wear on the rover’s six aluminum wheels, on which holes and tears became noticeable in 2013, raising concerns but so far not impairing the mission. Curiosity also recorded panoramic scenes from the highest viewpoints it has reached in its 44-month journey. –Elise Ricard

Moon Over Makemake

For the time being, five objects in our solar system are known as dwarf planets, a classification created by astronomers in 2006 for small objects orbiting the Sun that are massive enough to be roughly spherical, but which have not gravitationally dominated their orbits. This status may eventually change as astronomers find new objects that fit the criteria (the list of dwarf planet candidates continues to grow), but the group currently includes Ceres, the only dwarf planet in the inner solar system, and four objects way out in the Kuiper Belt beyond Neptune—Pluto, Eris, Haumea, and Makemake. Three of these are known to have moons.

Okay, make that four.

Well, four have natural moons—Ceres has an artificial satellite, namely NASA’s Dawn spacecraft, which has been orbiting for more than a year. On the other hand, the former-planet Pluto has a whopping retinue of five companions—Charon, Nix, Hydra, Kerberos, and Styx, all named after Greek mythological figures associated with death or the underworld. Eris, named for the Greek goddess of discord, is nearly the same size as Pluto but has only one known moon, which was discovered in 2005 and eventually named Dysnomia, after Eris’ daughter, the goddess of lawlessness. Haumea, named for a Hawaiian goddess of fertility, has two moons—Hi’iaka and Namaka, also discovered in 2005.

On Tuesday, April 26, astronomers announced the discovery of a moon orbiting Makemake, based on observations that took place in April 2015 using the Wide Field Camera 3 instrument on the Hubble Space Telescope, which can pick out faint objects next to very bright ones. This allowed allowed astronomers to image a small, dark body that is a mere 1/1300 as bright as Makemake itself. Provisionally designated S/2015 (136472) 1 and nicknamed “MK 2” (thank goodness), the little moon measures approximately 160 kilometers (100 miles) in diameter and orbits at a distance of 21,000 kilometers (13,000 miles). From Makemake, MK 2 would appear slightly smaller than our own Moon does from Earth.

Makemake was discovered in 2005 by a team led by Michael Brown of the California Institute of Technology, who also discovered Eris, Haumea, and Haumea’s moons. It was initially named 2005FY9, then later officially renamed for a creation deity of the Rapa Nui people of Easter Island. Brown was a content advisor the the current Morrison Planetarium feature Incoming! –Bing Quock

Tailless Comet

Deep in the reaches of the outer Solar System, astronomers have uncovered an incongruous comet that may hold hints to the formation of Earth and the other rocky inner planets.

Dubbed C/2014 S3, the comet is a small and rocky body, and it seems to have been perturbed recently from an orbit in the Oort cloud. This region is filled with long-period comets (with orbital periods longer than 200 years), and although interactions between them are thought to be rare, such events could send the small objects tumbling closer to the Sun. That means C/2014 S3 has just been forced from the deep freeze at a distance of about 1,000 astronomical units (or 1,000 times as far from the Sun as Earth) into the comparatively balmy inner solar system, 500 times closer. This alone might make the object noteworthy, but as it approached the Sun, astronomers noticed an anomalous and surprising detail: Comet C/2014 S3 failed to manifest a tail!

Based on the color and amount of sunlight that we see bouncing off the rocky body, C/2014 S3 seems to resemble the asteroids known as S-type, which are most commonly found in the inner solar system’s asteroid belt. The comets of the Oort cloud are usually thought of as icy and rich in tail-making materials. Astronomers have dubbed this tailless comet after tailless Manx cats—making C/2014 S3 a sort of prototypical new “species” of comet.

Why is this so revelatory? We have seen many rocky S-type asteroids, and we know they share a history with Earth, but they have also been subjected to harsh solar radiation for billions of years. Comet C/2014 S3 was born in the inner solar system, but it appears to have been flung out early on and preserved far from the Sun. It now provides invaluable insight that might start to settle conflicting theories of how our solar system developed. If the materials contained within C/2014 S3 has the right ratio of ices to rock, we will be able to confirm that the “giant planets danced across the Solar System when they were young, or if they grew up quietly without moving much,” according to Olivier Hainaut, co-author on a new paper about C/2014 S3.

The PanSTARRS survey discovered this and many other comets by taking wide photographic surveys of the sky several times a month and analyzing anything that changed in between photos. These digital surveys are similar in many ways to the photographic plates that Clyde Tombaugh used to discover another distant solar system object: the dwarf planet Pluto. Pluto and the other remote travelers in our solar system can teach us about the age of planetary formation around our shared star. –M. Josh Roberts

Transiting Moons

So far, no exomoons (moons orbiting planets orbiting other stars) have been confirmed. And from what we understand of planetary systems, Kepler-32 seems unlikely to have have them. However, UC Santa Cruz’s Michael Nayak has determined this unlikely system could actually harbor moons.

At 1,300 light years from Earth, Kepler-32 is very different from our own solar system. “The Kepler-32 system is the prototypical example of a new generation of solar systems that we are just now discovering: solar systems with several planets jammed very close—almost impossibly close—to their parent star,” Nayak says.

Just how close are they? “The closest planet to the star, Kepler-32f, is so close to its star that a ‘year’ on that planet is a mere 18 hours, or three quarters of a day,” he says. “That planet is approximately Mars-sized, but speeds around the star so fast that relativistic effects influence its orbit as much as gravitational effects. A year on the next three planets, Kepler-32e, b and c, are roughly three, six, and nine days long. The farthest planet is Kepler-32d, which has a relatively long year of 22.7 days. These four planets are all larger than the Earth, ranging from 1.5-2.7 Earth radii.”

That’s why there shouldn’t be a moon, Nayak says. “Because there’s so much mass crammed so close together, our traditional understanding tells us that any moon would have either been slung out of the solar system long ago, or accreted to one of these large planets.” But his simulations of Kepler-32’s gravity demonstrate otherwise. “I’ve found that ‘exo-moons’ may exist around one or more of the Kepler-32 planets. Which is very surprising! Because of the constant gravitational pull of so many planets, the moons are frequently snatched out of orbit around one planet. They enter a comet-like orbit around the star, and decades later, are sucked back into orbit around another planet, making them ‘transiting’ moons.”

Nayak presented his findings in under three minutes last week at the University of California Grad Slam competition. Taking the top spot among Santa Cruz graduate students, Nayak then competed against students from the nine other UC campuses. “I entered the Grad Slam to try and bring my research to more people. Planetary science and astrophysics can seem intimidating sometimes—people think it’s all scary math and tough equations. To inspire people to make the next discoveries, they need to know the ‘cool factor’ that makes it all worth it!”

It’s very cool. Nayak’s research highlights just how important moons are. “Moons have a large impact on the geology and orbital stability of the planets they orbit,” he says. “For example, I’m working to figure out the maximum mass that one of these exomoons could be. Why is that important? Well, compare Mars and Earth. Both have moons—but ours is planet-sized, and Mars’s are asteroid-sized. We now think that in the ancient past, Mars had water on the surface. But because of the changing obliquity of Mars (planet tilt), the climate changed rather violently—as a result, at one point, Mars’s poles were warmer than the equator! But that never happened on Earth, because every time the Earth’s obliquity tries to swing, our Moon damps that right out— keeping our climate relatively stable. Mars’s moons are too small to do that. That’s just one example of how moons can change a planet’s fate… while I’m not saying that is what happens at Kepler-32, the more we know about these moons, the more we can tell about what that impact might be.” –Molly Michelson

​Image: Makemake and moon, Dan Tell/California Academy of Sciences