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<\/p>\nAs science teams and researchers spent 2017 pouring through the wealth of data returned by the New Horizons spacecraft during its historic flyby of the dwarf planet Pluto in July 2015, the spacecraft\u2019s controllers spent the year busily preparing the craft for its anticipated flyby of Kuiper Belt Object 2014 MU69 \u2013 a flyby event scheduled for exactly one year from today on 1 January 2019.\n<\/p>\n
While New Horizons spent five months of 2017 in hibernation, its teams did anything but. The year saw a dedicated ground-based campaign on Earth to observe flyby target MU69 as it occulted a distant star to determine a better estimate for its size, mass, shape, and near space environment \u2013 an observational campaign designed to help the New Horizons team gather better information on the object to help plan precisely how and at what distance the craft will fly by the distant object next year. <\/p>\n
The campaign, previously reported by NASASpaceflight.com, revealed MU69 to be much weirder than first thought \u2013 with the Kuiper Belt Object now believed to be either two distinct objects orbiting each other or a close\/contact binary \u2013 meaning the object is two separate hunks of rock that orbit each other extremely close or actually touch each other. \u201cThis new finding is simply spectacular. The shape of MU69 is truly provocative and could mean another first for New Horizons going to a binary object in the Kuiper Belt,\u201d said Alan Stern. \u201cI could not be happier with the \u2026 results, which promise a scientific bonanza for the flyby.\u201d<\/p>\n
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Now you see it, now you don\u2019t. Kuiper Belt Object 2014 MU69 \u2013 4.1 billion miles from Earth \u2013 briefly blocks the light from a background star as seen from a mobile telescope in Argentina on 17 July 2017. Credits: NASA\/JHUAPL\/SwRI<\/p>\n
Based on the ground-based observations in 2017, MU69 now appears to be no more than 20 miles (30 kilometers) long, or, if it\u2019s a binary, each pair is about 9-12 miles (15-20 kilometers) in diameter. \u201cThese exciting and puzzling results have already been key for our mission planning,\u201d said Marc Buie, a New Horizons science team member at the Southwest Research Institute, \u201cbut also add to the mysteries surrounding this target leading [up to] the New Horizons encounter.\u201d<\/p>\n
The information gathered from a fleet of telescopes deployed on the ground in South Africa and Argentina and airborne over the Pacific with NASA\u2019s SOFIA telescope gave New Horizons\u2019 mission planners the data needed to create a primary science objective flight path for the MU69 flyby. That milestone will mark the farthest celestial object encounter in history \u2013 more than four billion miles (6.5 billion km) from Earth and more than one billion miles (1.5 billion km) beyond Pluto. If all goes as planned, New Horizons will pass just 2,175 miles (3,500 km) over MU69, peering down on it from celestial north. <\/p>\n
If this close approach is executed, the highest-resolution camera on New Horizons, the telescopic Long Range Reconnaissance Imager should be able to spot details as small as 230 feet (70 m) across, compared to nearly 600 feet (183 m) on Pluto. An alternate plan, to be employed in certain contingency situations such as the discovery of debris near MU69, would take New Horizons within 6,000 miles (10,000 km) of the object \u2013 still closer than the 7,800 mile (12,500 km) flyby distance at Pluto. <\/p>\n
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Artist\u2019s impression of MU69 with its suspected moon as seen during New Horizons\u2019 planned 1 January 2019 flyby event. Credits: NASA\/JHUAPL\/SwRI<\/p>\n
Moreover, as the year came to a close, scientists were intrigued by data not seen in the first review of information gathered from the Earth-based observation campaign of MU69 during its occultation of a distant star this year. In pouring through the data in detail, scientists were surprised and excited to see indications that MU69 might have an orbital companion: a small moon. \u201cWe really won\u2019t know what MU69 looks like until we fly past it, or even gain a full understanding of it until after the encounter,\u201d said Buie. \u201cBut even from afar, the more we examine it, the more interesting and amazing this little world becomes.\u201d<\/p>\n
The prospect that MU69 might have a moon comes from data collected by NASA\u2019s airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) on 10 July 2017 during the second of three occultation events observed this summer. Focused on MU69\u2019s expected location, SOFIA detected what appeared to be a very short drop-out in the star\u2019s light. Buie said further analysis of the data, including syncing it with MU69 orbit calculations provided by the European Space Agency\u2019s Gaia mission, opens the possibility that the \u201cblip\u201d SOFIA detected could be another object around MU69.<\/p>\n
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\u201cA binary with a smaller moon might also help explain the shifts we see in the position of MU69 during these various occultations,\u201d Buie added. \u201cIt\u2019s all very suggestive, but [it is] another step in our work to get a clear picture of MU69 before New Horizons flies by.\u201d Alan Stern added, \u201cThe occultation effort that Marc Buie and his team led for New Horizons has been invaluable in opening our eyes to the very real possibilities that MU69 is both a lot more complex than anyone suspected and that it holds many surprises for us at flyby on New Year\u2019s Eve and New Year\u2019s Day, 2019. The allure of its exploration is becoming stronger and stronger as we learn more and more about it. It\u2019s just fantastic!\u201d<\/p>\n
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New Horizons\u2019 journey through the solar system to its encounter with 2014 MU69 \u2013 formerly known a Potential Target 1 (PT-1). Credit: NASA<\/p>\n
But 2014 MU69 is not the only mission target New Horizons\u2019 scientists learned more about this year. Two and a half years ago, when New Horizons flew past the dwarf planet Pluto, the craft began returning a stream of data to Earth that took more than a year to fully transmit. With all the data from the flyby in hand for more than a year now, scientists have been busy examining everything observed by the craft, including information regarding strange blade-like terrain seen on the dwarf planet\u2019s surface.<\/p>\n
Among the many discoveries made by New Horizons on Pluto were strange formations resembling giant knife blades of ice. The series of bladed ridges on Pluto\u2019s surface, known as \u201cpenitentes,\u201d are bowl-shaped depressions with blade-like spires around the edge that rise several hundreds of feet above the local terrain. At the beginning of the year, research by John Moores of York University, Toronto, in collaboration with scientists at the Johns Hopkins University Applied Physics Laboratory and NASA Goddard Space Flight Center, showed that these icy features may also exist on other planets where environmental conditions are similar.<\/p>\n
The identification of these ridges in Pluto\u2019s Tartarus Dorsa area suggests that the presence of an atmosphere is necessary for the formation of penitentes \u2013 which Moores says would explain why they have not previously been seen on other airless icy satellites or dwarf planets. \u201cExotic differences in the environment give rise to features with very different scales,\u201d he adds. \u201cThis test of our terrestrial models for penitentes suggests that we may find these features elsewhere in the solar system and in other solar systems where the conditions are right.\u201d<\/p>\n<\/p>\n