The brilliantly successful New Horizons that flew by Pluto in a spectacular reconnaissance mission on 14 July last year closes out this month with two great stories.
New Horizons Spies a Kuiper Belt Companion
On its way to a New Years Day 2019 rendezvous with its next port of call, 2014 MU69, New Horizons is doing some sightseeing along the way. Spying the 1,100 Km wide Kuiper Belt Object whose radius is approximately 50% that of its larger cousin, Pluto, Quaoar was at a distance of 2.1 billion Km in mid-July, the intrepid space craft was 6.4 billion Km from the sun or as far from Pluto as Jupiter is from the Earth! New Horizons’ location in the Kuiper Belt gives the spacecraft a unique view of the small planets like Quaoar orbiting so far from the sun. With the oblique view only available from New Horizons on its current trajectory, LORRI (Long Range Reconnaissance Imager) sees only a portion of Quaoar’s illuminated surface, a view quite different from the nearly fully illuminated view as would be from Earth. Comparing Quaoar from the two very different perspectives gives mission scientists a valuable opportunity to study the light-scattering properties of Quaoar’s surface. What heightens the interest in this animated composite is the serendipitous background location of two distant galaxies in the field of view, IC 1048 and UGC 09485. Located in the constellation Virgo, these galaxies are both about about 75 million light years distant or about 370 billion times more distant than New Horizons. On its current course and trajectory, New Horizons is outbound, headed in the direction of the constellation Virgo!
Pluto’s Methane Snowcaps on the Edge of Darkness
This area is south of Pluto’s dark equatorial band informally named Cthulhu Regio, and southwest of the vast nitrogen ice plains informally named Sputnik Planitia. In this view, North is at the top and in the western portion of the image, a chain of bright mountains extends north into Cthulhu Regio. New Horizons compositional data indicate the bright snowcap material covering these mountains isn’t water, but atmospheric methane that has condensed as frost onto these surfaces at high elevation. Between some mountains are sharply cut valleys – indicated by the white arrows. These valleys are each a few miles across and tens of miles long.
A similar valley system in the expansive plains to the east appears to be branched, with smaller valleys leading into it. It is thought that flowing nitrogen ice that once covered this area — perhaps when the ice in Sputnik was at a higher elevation — may have formed these valleys. The area is also marked by irregularly shaped, flat-floored depressions (green arrows) that can reach more than 80 Km (50 mi) across and almost 3 Km (2 mi) deep. The great widths and depths of these depressions suggest that they may have formed when the surface collapsed, rather than through the sublimation of ice into the atmosphere.
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