The space images were obtained by the New Horizons probe

Oct 6, 2015 19:26 GMT  ·  By

New space images released by NASA this past Monday, October 5, bring into focus two of Pluto's smaller moons, Nix and Hydra. 

Together with the dwarf planet, the orbs were imaged by the New Horizons probe earlier this year, on July 14, during its flyby of the Pluto system.

The moons were only recently discovered

Dwarf planet Pluto was discovered by astronomer Clyde Tombaugh back in February 1930. As it turns out, it took a while for the scientific community to also spot the moons orbiting it.

Thus, Charon, the biggest of the bunch, was documented in June 1978. Nix and Hydra went unnoticed until 2005, just months before the launch of the New Horizons spacecraft, and Styx and Kerberos were only discovered in 2011 and 2012, respectively.

As mentioned, Charon is Pluto's largest moon. It's about half the size of the dwarf planet, and scientists describe it as ball carrying mountains, canyons, craters and even ridges on its surface.

By comparison, Pluto's other moons, the teeny tiny Nix, Hydra, Styx and Kerberos, are far from being perfect spheres. Rather, they look more like space boulders circling the dwarf planet.

Astronomers say this is because, since they all measure less than 30 miles (50 kilometers) across at their widest, there is no gravity to mold them in the shape of spheres.

“Each has a lumpy shape because, unlike Pluto and Charon, they aren’t big enough for gravity to squish them into a ball,” explains NASA researcher Simon Porter.

Mind you, this doesn't make them any less interesting

They might look more like potatoes than proper moons, but this doesn't mean Nix, Hydra, Styx and Kerberos are any less interesting and so don't deserve their moment in the limelight.

On the contrary, images beamed back by NASA's New Horizons probe show that, at some point in its history, Nix survived a collision with another celestial body. Hence the large crater visible on its surface.

Interestingly, this newly discovered impact crater on Nix has researchers wondering if perhaps the moon might not be part of a larger orb that was destroyed many millennia ago.

“Nix isn't very large, and there is a very fine line between an impact that will make a crater that big and one that will break Nix apart. So either Nix was very lucky in surviving that collision, or it's a fragment of an older moon that was somehow destroyed.”

As for Pluto's moon Hydra, scientists say that, judging by the views delivered by the New Horizons probe, the orb kind of, sort of resembles Comet 67P/Churyumov-Gerasimenko, in turn said to be shaped like a duckling. Its silhouette suggests it formed when two smaller moons collided and morphed into just one celestial body.

NASA views of the Pluto system (8 Images)

Artist's rendering of NASA's New Horizons probe
Pluto's moon NixNew Horizons views of Nix
+5more