New color images taken by NASA’s New Horizons spacecraft have revealed four unusual dark spots evenly spaced along the equator of Pluto, each about the same size as the state of Missouri.
The scientists in charge of the mission said that they haven’t seen anything like these dark spots, which the Los Angeles Times said are all approximately 300 miles in diameter. However, NASA said that they have “piqued the interest” of the New Horizons team due to the consistency in the spacing and size of the spots. Their origin, for now, remains unknown.
“It’s a real puzzle – we don’t know what the spots are, and we can’t wait to find out,” principal investigator Alan Stern from the Southwest Research Institute in Boulder, Colorado, said in a statement Wednesday. “Also puzzling is the longstanding and dramatic difference in the colors and appearance of Pluto compared to its darker and grayer moon Charon.”
Stern and his colleagues combined black-and-white images of Pluto and its moon Charon captured with the probe’s Long-Range Reconnaissance Imager (LORRI) instrument with lower-resolution infra-red data from its Ralph instrument to produce the new images. The objects are shown in nearly true color, or how they would appear to someone riding on New Horizons.
According to the Times, the images reveal that Pluto’s tan surface is far lighter than the gray-colored Charon, and that difference in color also has piqued the interest of researchers. The New Horizons probe is now less than 9.5 million miles from the Pluto system, and is on schedule to make its closest approach of 7,700 miles away from the planet’s surface on July 14.
The spacecraft is currently using its high-resolution LORRI imager and the Ralph color imager to search for clouds on Pluto, NASA said. Science team member Kelsi Singer of the Southwest Research Institute said that they were using “a number of techniques” to find clouds in images. If found, those clouds make it possible “to track the speeds and directions of Pluto’s winds.”
In addition, the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on board New Horizons is also transmitting data of the space environment surrounding Pluto on a daily basis. PEPSSI, NASA explained, is being used to find out the composition of ions that are escaping from Pluto’s atmosphere, and to determine how quickly ions (atoms that have gained or lost electrons) are getting caught up in the dwarf planet’s solar wind.