Ijzige pieken op kleine planeet
De volgende opmerkelijke verschijnselen op het hemellichaam aan de rand van ons zonnestelsel zijn genoteerd op basis van de eerste gegevens die men kon analyseren.. De voorbije week leverde dat een serie eerste items en updates op en tot ver in 2016 moeten beelden en data nog verwerkt worden door de NASA, zodat nog veel nieuwere inzichten en verrassingen mogelijk zijn. Vier pinten daarom nu vast vanuit de eerste berichten over Pluto.
1] Pluto’s icy mountains have company. NASA’s New Horizons mission has discovered a new, apparently less lofty mountain range on the lower-left edge of Pluto’s best known feature, the bright, heart-shaped region named Tombaugh Regio, situated between bright, icy plains and dark, heavily-cratered terrain. (The names of features on Pluto have all been given on an informal basis by the New Horizons team.)
These newly-discovered frozen peaks are estimated to be one-half mile to one mile (1-1.5 kilometers) high, about the same height as the United States’ Appalachian Mountains. The Norgay Montes (Norgay Mountains) discovered by New Horizons on July 15 more closely approximate the height of the taller Rocky Mountains.
2] Peering closely at the “heart of Pluto,” in the western half of what mission scientists have informally named Tombaugh Regio, New Horizons’ Ralph instrument revealed evidence of carbon monoxide ice. The contours indicate that the concentration of frozen carbon monoxide increases towards the center of the “bull’s eye.” These data were acquired by the spacecraft on July 14 and transmitted to Earth on July 16.
3] “There is a pronounced difference in texture between the younger, frozen plains to the east and the dark, heavily-cratered terrain to the west,” said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA’s Ames Research Center in Moffett Field, California. “There’s a complex interaction going on between the bright and the dark materials that we’re still trying to understand.”
While Sputnik Planum is believed to be relatively young in geological terms – perhaps less than 100 million years old – the darker region probably dates back billions of years. Moore notes that the bright, sediment-like material appears to be filling in old craters.
4] New Horizons Ralph instrument also reveals an abundance of methane ice, but with striking differences from place to place across the frozen surface of Pluto.
“We just learned that in the north polar cap, methane ice is diluted in a thick, transparent slab of nitrogen ice resulting in strong absorption of infrared light,” said New Horizons co-investigator Will Grundy, Lowell Observatory, Flagstaff, Arizona. In one of the visually dark equatorial patches, the methane ice has shallower infrared absorptions indicative of a very different texture. “The spectrum appears as if the ice is less diluted in nitrogen,” Grundy speculated “or that it has a different texture in that area.”
