It has been nearly a month and a half since the historic flyby of Pluto by the New Horizons spacecraft, and now the mission team has selected its next target for exploration: a small Kuiper Belt object (KBO) known as 2014 MU69, which orbits the Sun about a billion miles farther than Pluto. This will be the first time such a remote object in the Kuiper belt has been visited by a spacecraft from Earth.
“Even as the New Horizon’s spacecraft speeds away from Pluto out into the Kuiper Belt, and the data from the exciting encounter with this new world is being streamed back to Earth, we are looking outward to the next destination for this intrepid explorer,” said John Grunsfeld, astronaut and chief of the NASA Science Mission Directorate at the agency headquarters in Washington. “While discussions whether to approve this extended mission will take place in the larger context of the planetary science portfolio, we expect it to be much less expensive than the prime mission while still providing new and exciting science.”
If all goes well, New Horizons is expected to reach 2014 MU69 on Jan. 1, 2019. 2014 MU69 was chosen out of two possible targets, although a detailed assessment will still need to be done before the mission extension is officially approved. The New Horizons team must first write a proposal to NASA to fund a KBO mission, due in 2016. The proposal will then be evaluated by an independent team of experts before the mission extension gets approval to go ahead.
It was recommended by the 2003 National Academy of Sciences’ Planetary Decadal Survey (“New Frontiers in the Solar System”) that this first mission to the Kuiper Belt should include flybys of both Pluto and other KBOs in order to maximize the science return. It would be a great opportunity to investigate objects such as KBOs that had never been visited before.
2014 MU69 should be an ideal KBO to study, since it represents the kind of rocky objects which formed so far from the Sun and have remained virtually unchanged over billions of years. KBOs are similar to asteroids in the main asteroid belt between Mars and Jupiter, but are colder and better preserved since their formation billions of years ago.
According to New Horizons Principal Investigator Alan Stern: “2014 MU69 is a great choice because it is just the kind of ancient KBO, formed where it orbits now, that the Decadal Survey desired us to fly by. Moreover, this KBO costs less fuel to reach (than other candidate targets), leaving more fuel for the flyby, for ancillary science, and greater fuel reserves to protect against the unforeseen.”
Since New Horizons was designed to do just this kind of a post-Pluto mission, it has extra fuel on board and its communications system can continue to work at distances much farther than Pluto.
Smaller objects like KBOs are not easy to detect from Earth; a search was started in 2011 using ground-based telescopes, and several dozen KBOs were found, but none of them were ideal since they were not reachable by the spacecraft. But then, five new potential targets were discovered by the Hubble Space Telescope in 2014. That list was then reduced to the two best choices, including 2014 MU69. 2014 MU69, also known as Potential Target 1 (PT1), is tiny, estimated to be just under 30 miles (45 kilometers) in diameter, which is only about 0.5 to 1 percent of the size (and 1/10,000th the mass) of Pluto. Such KBOs are thought to be the original building blocks of larger dwarf planets like Pluto in the Kuiper Belt.
“There’s so much that we can learn from close-up spacecraft observations that we’ll never learn from Earth, as the Pluto flyby demonstrated so spectacularly,” said New Horizons science team member John Spencer, of the Southwest Research Institute (SwRI) in Boulder, Colo. “The detailed images and other data that New Horizons could obtain from a KBO flyby will revolutionize our understanding of the Kuiper Belt and KBOs.”
The Kuiper Belt was named after Gerard Kuiper, who first theorized its existence. Over 1,000 KBOs have been identified so far, including Pluto, but many more are also expected to be discovered.
New Horizons has sent back incredible images of Pluto and its moons, with many more to come after the data “pipeline” reopens around Sept. 5. After that there will be a continuous stream of data being sent back to Earth for several months, which is currently still being stored on the spacecraft since its historic flyby of Pluto on July 14. Only about 5 percent of the total data has been returned to Earth so far.
The images show Pluto to be an active, dynamic world, with glacier-like features composed of nitrogen ice which slowly flow across the surface, similar to glaciers on Earth. There may also be active cryovolcanism where the nitrogen is replenished onto the surface from below. Pluto’s thin atmosphere is also primarily composed of nitrogen. Methane and carbon monoxide ices have also been found on Pluto, concentrated in the large prominent “heart-shaped” feature. The lack of craters on much of Pluto’s surface indicates current, ongoing geological activity. At this distance from the Sun, water ice is as hard as rock, but farther down there may even be a subsurface ocean, according to current research, although that is still unconfirmed at this point.
Pluto’s largest moon Charon also shows signs of geological activity, including deep canyons, although probably not as recent. Overall, the Pluto system is a more active place in many ways than was previously thought. What surprises might be found at other KBOs? The only way to find out is to go there.
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