New Horizons Takes a Nap

            NASA’s New Horizons spacecraft is about to take a well-deserved nap. The spacecraft has been in continuous operation since December 2014 as it prepared for its rendezvous with Pluto in July 2015. On July 14, 2015 New Horizons came within 7,750 miles of Pluto’s surface, making it the closest approach by a manmade object to the dwarf planet. Almost immediately, the spacecraft began transmitting its photographs and other data, totaling 6.25 gigabytes, back to Earth. The download process lasted from July 16, 2015 through October 25, 2016. Due to the distance between New Horizons and Earth and slow rate of transmission, it takes approximately four and a half hours to send one image from the spacecraft to researchers.  With this download process finally complete, NASA has put New Horizons into hibernation until September 2017 with another hibernation likely in 2018, before an encounter with a mysterious object in the Kuiper Belt called MU69.        

The 7.2 ft. by 6.9 ft. by 8.9 ft., thousand-pound spacecraft carries seven scientific instruments in total. These include three optical instruments, two plasma ones, a dust sensor and a radio receiver/transmitter. Combined the instruments have made thousands of observations of Pluto’s geology, surface composition, temperature, atmospheric pressure, and atmospheric temperature. New Horizons has two computer systems, one for command and handling of the spacecraft and the other for guidance. A single radioisotope thermoelectric generator (RTG) supplied by 24 pounds of plutonium dioxide powers the entire spacecraft. The remarkable photographs, like those shown below, come from the Long Range Reconnaissance Imager (LORRI).

Pluto, up close and personal

The surface of Pluto 

Pluto's moon, Charon 

Using the data collected and analyzed so far, NASA released a list of the top ten discoveries uncovered by New Horizons so far. These included:

• The complexity of Pluto and its satellites is far beyond what we expected. 
• The degree of current activity on Pluto's surface and the youth of some surfaces on Pluto are simply astounding. 
•  Pluto’s atmospheric hazes and lower-than-predicted atmospheric escape rate upended all of the pre-flyby models.
•  Charon’s enormous equatorial extensional tectonic belt hints at the freezing of a former water ice ocean inside Charon in the distant past. Other evidence found by New Horizons indicates Pluto could well have an internal water-ice ocean today.
• All of Pluto’s moons that can be age-dated by surface craters have the same, ancient age—adding weight to the theory that they were formed together in a single collision between Pluto and another planet in the Kuiper Belt long ago.
• Charon’s dark, red polar cap is unprecedented in the solar system and may be the result of atmospheric gases that escaped Pluto and then accreted on Charon’s surface.
• Pluto’s vast 1,000-kilometer-wide heart-shaped nitrogen glacier (informally called Sputnik Planum) that New Horizons discovered is the largest known glacier in the solar system.
• Pluto shows evidence of vast changes in atmospheric pressure and, possibly, past presence of running or standing liquid volatiles on its surface – something only seen elsewhere on Earth, Mars and Saturn’s moon Titan in our solar system.
• The lack of additional Pluto satellites beyond what was discovered before New Horizons was unexpected.
• Pluto's atmosphere is blue. 

Now as New Horizons heads towards its date with MU69 in early 2019, we say, enjoy your nap little friend, you’ve earned it.