WORLD | Way out there | Julie Borg | April 16, 2016

The enigma of Pluto the planet. When I was very young I knew of Pluto to be a cartoon dog . As I went t elementary school I learned that Pluto was the furthest, smallest and coldest of the planets in the solar system. A few years ago I was amused to learn that astronomers had demoted Pluto from Planet status.
"NASA’s New Horizons spacecraft zipped by Pluto on July 14 last year, giving astronomers their first close-up look at the far-off dwarf planet. The spacecraft has been beaming data back to Earth ever since. Although only half the information is in, planetary scientists published their initial Pluto discoveries last month.
So far the little world has posed to scientists a multitude of unsolved mysteries.
For example, the smooth, 650-mile-wide icy plain known as Sputnik Planum is unmarred by craters, yet impact depressions pockmark the nearby highlands.
Pluto’s ice mountains present their own conundrum. On the plain, nitrogen, methane, and carbon monoxide cycle between frozen and gaseous states, creating flowing glaciers of mostly nitrogen ice on a foundation of water ice. But scientists can’t explain how the soft nitrogen ice has carved the much harder water ice into towering mountains.
Scientists are also baffled by Pluto’s deep valleys. The dwarf planet’s average temperature of minus 400 degrees Fahrenheit is too cold for nitrogen, Pluto’s main element, to become a fluid that could carve such gorges.
Another mystery: How does such a small dwarf planet retain its atmosphere? Scientists predicted Pluto’s nitrogen would be gushing away into space, but instead New Horizons found a mere trickle, 10,000 times less than expected.
“Pluto’s really tiny, so it doesn’t have the mass to hold on to an atmosphere over the age of the solar system—at least we wouldn’t have thought that,” Randy Gladstone of San Antonio’s Southwest Research Institute told New Scientist.
The recent Pluto studies were published in the March 18 edition of Science. Researchers expect the remaining New Horizons data to be available later this year." SSgt (Join to see) SrA Christopher Wright SrA Edward Vong PO2 Ed C. PO3 Steven Sherrill