Researchers analyzing an image captured by NASA’s New Horizons spacecraft shortly after it made its closest approach to Pluto have discovered what could be the first-ever cloud located in the dwarf planet’s atmosphere, the US space agency announced earlier this week.
The image, captured by the probe on July 14, 2015, was obtained at a high-phase angle, meaning that the sun was on the opposite side of Pluto relative to New Horizons’ position. Using sunlight filters, it was able to peer through and illuminate the dwarf planet’s atmospheric haze layers over the part of the planet’s surface informally known as the “Twilight Zone.”
In addition to depicting the southern part of the nitrogen ice plains called Sputnik Planum and the mountain range known as the Norgay Montes, this newly-released photo shows what officials at the agency refer to as “an intriguing bright wisp,” tens of miles in length, that they believe could be a “discreet, low-lying cloud,” which would make the first ever identified in an image captured by New Horizons during its fly-by of the dwarf planet.
New Horizons used its Ralph/Multispectral Visual Imaging Camera (MVIC) to obtain the image from a distance of approximately 13,400 miles (21,550 kilometers) from Pluto, about 19 minutes after making its closest approach to the dwarf planet. Photographs such as this one, which has a resolution of 1,400 feet (430 meters) per pixel, helps provide new insight into the planet’s hazes and surface properties, the agency explained.
So why was this wisp visible in this particular picture?
If this is indeed a cloud, NASA scientists explained that it is visible for the same reason that the haze layers in the dwarf planet’s atmosphere appear to be so bright: sunlight illuminates them as is grazes the surface at a low angle. Atmospheric models have suggested that methane clouds can form in Pluto’s atmosphere from time to time, and this may well be one of them.
Another image captured by the spacecraft shows the night side of Pluto in greater detail, as this part of the dwarf planet’s terrain is illuminated from behind by various hazes. The picture shows a rugged terrain with vast valleys and sharp mountains with relief totaling three miles (5 km).
Since the image was taken at a closer distance than previous ones depicting the area, it is higher in resolution, enabling scientists to use it as a sort of “anchor point” to get a good look at the lay of the landscape in this typically obscured part of the dwarf planet. The image shows a 460 mile (750 km) wide part of the Pluto landscape typically visible in high resolution only at twilight.
According to Space.com, New Horizons will continue to beam data from its Pluto flyby back to Earth through the fall. It is currently more than three billion miles (5 billion km) away, meaning that transmission times are on the slow side as the spacecraft continues moving towards its next target, a tiny object known as 2014 MU69 that is roughly one billion miles (1.6 billion km) away from the Earth.
Image credit: NASA