Recent findings from the New Horizons team reveal that Pluto’s third-largest satellite Nix is covered in the purest water ice yet observed in the dwarf planet system, even purer in spectra than what was seen on its slightly larger sibling Hydra. This analysis further supports the hypothesis that Pluto’s moons were created in an impact event that formed the Pluto-Charon system, over 4 billion years ago.
Discovered in June 2005, distant Pluto’s outermost moon Hydra it thought to have formed during the same collision four billion years ago that created the Pluto-Charon system that we see today. Yet despite its age this 31-mile (50-km) -long moon appears remarkably clean and bright, as witnessed by New Horizons during its close pass through the Pluto system in July 2015.
When New Horizons made its close pass pf Pluto on July 14, 2015, it did much more than just take pretty pictures; it was also scanning the planet with a suite of science instruments designed to determine the nature of its surface, atmosphere, composition, and other key characteristics. One of these instruments was the Linear Etalon Imaging Spectral Array (LEISA), an infrared scanner that can detect the unique molecular “fingerprints” of particular elements and compounds like methane, nitrogen, carbon monoxide… and water (one of our favorites!)
At first the data returned from LEISA showed only a surprisingly small amount of water ice across Pluto’s surface. But that was water ice in its pure form; when researchers took into consideration ice containing a mixture of water and other materials they found a much more widespread distribution across the surface area visible to New Horizons.
Here’s a view of a section of a crater on Mars filled with a lacework of bright spidery fractures, acquired on Sept. 20, 2015 with the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter. The crater is approximately 3 miles (5 km) wide and located in Mars’ north polar region, and its old, infilled interior has undergone countless millennia of freeze/thaw cycles that have broken the surface into polygons of all sizes, outlined by frost-filled cracks.
The fractured segments get increasingly more compressed closer to the crater rim, which contains the outward freeze expansion.
According to the image description from the HiRISE team:
The crater rim constrains the polygon formation within the crater close to the rim, creating a spoke and ring pattern of cracks. This leads to more rectangular polygons than those near the center of the crater. The polygons close to the center of the crater display a more typical pattern. A closer look shows some of these central polygons, which have smaller polygons within them, and smaller polygons within those smaller polygons, which makes for a natural fractal!
Source: HiRISE/University of Arizona
Now over four months after the historic and long-awaited flyby of Pluto by New Horizons, planetary scientists have had a steady stream of unprecedented data arriving on Earth from the outwardly-speeding spacecraft. We’ve learned more about Pluto in the past few months than we had over the decades before and the information is still being analyzed — and is still coming. This surprising little world and its strange family of mismatched moons, 33 times farther from the Sun than us, has become in the latter half of 2015 the scientific “star of the Solar System.” (Take that all you can’t-be-a-planet folks!)
“It’s hard to imagine how rapidly our view of Pluto and its moons are evolving as new data stream in each week. As the discoveries pour in from those data, Pluto is becoming a star of the Solar System. Moreover, I’d wager that for most planetary scientists, any one or two of our latest major findings on one world would be considered astounding. To have them all is simply incredible.”
– Dr. Alan Stern, New Horizons Principal Investigator, SwRI
So now that NASA’s Dawn spacecraft has been in orbit around Ceres for seven months, has the nature of its strange bright spots finally been determined? Are they brilliantly reflective deposits of water ice, as many initially suspected? Or just some curiously-bright rock faces? (Or the metallic remains of an ancient alien space base, like more than a few folks have imagined?) As it turns out, Ceres’ bright spots may be none of these (and especially not that last one… puh-leeze) — they may be enormous deposits of salt.