A new batch of NASA pictures from Pluto's surface has baffled astronomers who are attempting to explain the presence of methane ice on the icy planet's "halo" craters. The photos - released April 21 - reveal that the one-of-a-kind craters are located in the west area of Pluto.
"Within Pluto's informally named Vega Terra region is a field of eye-catching craters that looks like a cluster of bright halos scattered across a dark landscape," NASA said.
The images were captured by NASA's New Horizons spacecraft, which took the photos on the far west region of the planet at approximately 28,000 miles and 196,700 miles from the planet on July 14, 2015.
One of the most unique images captured numerous halo craters, with the biggest of the lot measuring around 50 miles across. The mysterious area possesses dark floors, which makes the bright walls and crater rims stand out, leading to the halo effect.
In addition, the New Horizons photoset also captures a crater that looks to connect the bright haloes with the methane ice that exists in the composition of the crater's terrain and floor.
NASA conducted analysis on the bright areas and confirmed a composition of methane and water. The findings are baffling because previous research suggests that methane does not settle anywhere in the rims and walls of Pluto's craters.
"Exactly why the bright methane ice settles on these crater rims and walls is a mystery; also puzzling is why this same effect doesn't occur broadly across Pluto," the agency said in a press release.
Despite the mystery of the methane ice, the bright snow is nothing new; in March, scientists captured images of snowcapped mountains made of methane tholins that were made visible against the darker surface region of Pluto's Cthulhu region. Although many were excited at the prospect of snow on the planet, the team made it clear that snow on Pluto would be much different than snow on Earth.
"Methane ice may act like water in Earth's atmosphere, condensing as frost at high altitude," said John Stansberry, a New Horizons science team member.
The images were captured using the New Horizons' Long Range Reconnaissance Imager (LORR).
