Pluto: ice plain and huge atmosphere

New Horizons data provide more surprises from the distant ice planet

The green mark shows the location and extent of the newly discovered ice level. She was informally christened "Sputnik Plain" - after the first artificial satellite of the earth. © NASA / JHUAPL / SwRI
Read out

Dwarf Planet with Giant Atmosphere: The New Horizons spacecraft has unveiled more surprising details about Pluto. So it has a wide, amazingly young layer of frozen carbon monoxide whose structure resembles dried mud. In addition, the dwarf planet has a surprisingly large atmosphere: it extends at least to 1, 600 kilometers altitude and is pulled out by the solar wind to a tail about 100, 000 kilometers long.

Just recently, New Horizons has transmitted shots of a very young iceberg on Pluto, now comes the next surprising information. In the latest images and data north of this ice mountains an extensive, crater-free plane can be seen. Their surface consists at least in part of frozen carbon monoxide, the thickness of which increases towards the center of the plane.

Strange floes and gutters

This ice level can not be more than 100 million years old, according to researchers from the New Horizons mission. Striking is their surface structure: It consists of approximately 20 kilometers of plaice, which are bounded by shallow channels. Some of these channels contain darker material, others are framed by hills.

In addition, in some areas, the interior of the plaice is littered with small holes, such as those typically found in sublimation of ice to water vapor. "The discovery of such a vast, crater-less, very young level surpasses all expectations, " said Jeff Moore, head of the mission's geology team. The recordings of the probe also showed dark stripes of several kilometers in length, which run in one direction over the floes. It may be material blown by the wind.

{2r} display

Creation of the floes mysterious

How this plane could have originated and what gave it its strange structure is still puzzling. "This terrain is not easy to explain, " says Moore. But researchers have two theories about it. The irregularly shaped fragments could have been caused by contraction of the surface, similar to a drying mud surface.

Alternatively, convection currents in the ice crust of Pluto could have led to these cracks and floes. A heat source inside the dwarf planet would then have to be the engine for these currents. According to previous knowledge, the crust of Pluto consists of frozen carbon monoxide, methane and nitrogen ice. The icy mountains, on the other hand, seem to consist of a particularly hard water ice.

Pretty huge atmosphere

The probe's measurements also show that Pluto has a rather extended atmosphere for its rather small size. The nitrogen-containing gas reaches up to 1, 600 kilometers altitude. The spectrograph aboard New Horizons was able to determine their extent by looking back after the flyby and analyzing Pluto's gas pocket in the back light of the sun.

"This is just the beginning of atmospheric research on Pluto, " says Andrew Steffl of the Southwest Research Institute in Boulder. "However, the data already show us that Pluto's atmosphere is relatively higher than that of Earth." The spacecraft has yet to transmit a small portion of its atmospheric data. The researchers expect the full set of backlight measurements next month.

New Horizons data indicates a long tail of ionized nitrogen. NASA / JHUAPL / SwRI

Solar wind creates gas tail

The atmosphere of the dwarf planet does not only seem to be big, but also quite fragile. Because New Horizons data shows that Pluto has a gigantic tail of ionized gas. On the side facing away from the sun, he falls on the "slipstream" of the dwarf planet, which reaches at least 109, 000 kilometers into space.

The tail is most likely generated by the solar wind. Even at this vast distance from our central star, this stream of high-energy particles and radiation still has an effect. At Pluto, the sun's ultraviolet light probably ionizes the nitrogen atoms of the atmosphere, and the solar wind carries them away with it. Similar plasma tails also have Venus and Mars.

How much of his gas pluto Pluto loses by this effect, could show more data of the probe. "In August, we will get more data from New Horizons, which we can then combine with previous ones to determine the loss rate, " explains Fran Bagenal of the University of Colorado at Boulder. "If we know that, then we can better answer questions about the evolution of the atmosphere on Pluto."

"So far, we've just scratched the surface of the data, " says mission scientist Alan Stern of the Southwest Research Institute. "But it seems to me already clear that we have the best for the conclusion of the exploration of the solar system."

(NASA / JHUAPL, 20.07.2015 - NPO)