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Update: Three APL Missions Focus on Solar System Origins

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One year after the Applied Physics Laboratory’s (APL) New Horizons spacecraft made its historic flyby of Pluto, the mission is on course to explore an even more distant object in what’s known as the Kuiper Belt.

At the same time, data collected by another of the north Laurel research center’s probes, MESSENGER, continues to shed light on the planet Mercury.

As if simultaneous exploration of the solar system’s innermost and outermost orbiting bodies weren’t enough, APL is also poised to begin exploring Jupiter, the midpoint planet between these two extremes, using an instrument aboard NASA’s JUNO probe.

All three missions are providing information that will significantly enhance humanity’s understanding of how the solar system formed and reveal much about the original materials present when formation began.

New Horizons

New Horizons provided the first clear pictures of Pluto and its moons in 2015.

“We were all mesmerized by the spectacular images, but those data weren’t completely suitable for scientific use because of the compression process used to reduce the number of bits downlinked,” said APL’s New Horizons Project Scientist Hal Weaver.

Even though APL began downlinking the data in full quality form in September 2015, it will take at least until the end of October 2016 to get all of the information back to earth, he said.

Currently, APL has successfully downloaded about 80% of the data New Horizons collected.

Included on APL’s list of top discoveries made possible by that data is the fact that Pluto’s atmosphere is blue, contains hazes and possesses a lower-than-predicted atmospheric escape rate. Scientists were also surprised by the degree of activity on Pluto’s surface, and by the youth of some of its surfaces. Among other findings, Charon’s tectonic belt hints at the freezing of a former water-ice ocean, while other evidence indicates Pluto may have its own internal water-ice ocean.

Scientists now know that the craters on Pluto’s moons are roughly the same age, suggesting that these bodies were likely formed together in a single collision between Pluto and another Kuiper Belt object in the distant past.

Additionally, Charon’s unique dark red polar cap may be the result of atmospheric gases escaping Pluto and accumulating on the moon’s surface.

Finally, Pluto joins Earth, Mars and Saturn’s moon Titan in displaying possible evidence of the past presence of running or standing liquid volatiles on its surface.

Next Stop: MU69

With NASA’s approval, the New Horizons team fired the spacecraft’s hydrazine thrusters in a series of maneuvers in October and November last year to put it on a trajectory to Kuiper Belt Object 2014 MU69. Closest approach will occur on Jan. 1, 2019.

“We’d like to get the best possible resolution, which means flying as close as possible,” Weaver said.

Preliminary analysis suggests a distance of about 1,800 miles might be optimal, taking the craft four times as close to MU69 as it passed by Pluto.

“Most of the science objectives … are identical to what we had for Pluto,” Weaver said. “The main exception is that we don’t really expect to detect an atmosphere. Otherwise, all of the New Horizons instruments will be probing MU69 just like they did for Pluto.”

Most exciting for the team is the prospect of exploring the most primitive body ever visited by a spacecraft mission.

“Primitive in this context means MU69 has retained the basic characteristics it was born with better than any of the other objects visited by previous spacecraft missions,” Weaver said. “MU69 may provide the best ever view of what the solar system was like 4.6 billion years ago.”

MESSENGER

In May, APL announced the release of the first global digital elevation model of Mercury, revealing topography across the entire planet in stunning detail and making it possible for scientists to characterize fully the planet’s geologic history.

According to APL’s Nancy Chabot, lead imaging scientist for MESSENGER, the new map will enable researchers to explore new questions. Among these: whether different geochemical or geological terrains on Mercury have associated topographical features, and whether a comparison of northern and southern hemisphere topography holds any implications for the planet’s geological evolution.

The MESSENGER imaging team is working to update and improve some of its products, refining the calibration of a five-color map of the northern hemisphere and improving the registration in images used to generate color mosaics of Mercury.

“The team is also completing a global geological map of Mercury, which will be the first of its kind,” Chabot said.

Scientists around the world are beginning to use MESSENGER’s data now that it is in the public domain.

“It is likely there are a number of [other] Mercury products being developed by members of the scientific community at large using this data,” she said.

The MESSENGER probe, sent to study Mercury’s chemical composition, geology and magnetic field, crashed into the planet in April 2015, following two mission extensions.

JEDI

NASAs Juno spacecraft entered Jupiter’s orbit on July 4, nearly five years after launch.

Among the instruments it carries is the Jupiter Energetic Particle Detector Instrument (JEDI), built by APL.

Consisting of three shoebox-sized detectors viewing different slices of Jupiter’s sky, the units provide a continuous 360-degree sampling view of the space around Juno. Their purpose is to detect electrons and ions, such as protons, helium, oxygen and sulfur, which interact with Jupiter’s atmosphere and create its aurora. The devices also measure energetic neutral atoms emanating from Jupiter’s auroral atmosphere.

“Jupiter’s aurora has a power density 10 times greater than Earth’s and an overall power that is a factor of 100 greater,” said JEDI Lead Investigator Barry Mauk, of APL. ‘What we want to know is, how is this system energized? Juno is going to help us really understand Jupiter and the fundamental physics of these important processes.”

Taken as a whole, Juno’s principal goal is to understand the origin and evolution of Jupiter, specifically focusing on how giant planets form and the role these bodies play in the formation of the rest of the solar system. That information is critical for understanding planetary systems now being discovered around other stars.

The JEDI team began formal science operations in January this year, long before Juno reached Jupiter, to investigate the planetary medium for so-called upstream ions that come from the planet and are not part of the solar wind.

“From what JEDI and the rest of the instruments on Juno will tell us, we should be able to understand more about the particles and radiation belts that we can observe around distant, more energetic objects like the Crab Nebula,” said Mauk. “Juno is not only going to help us better understand Jupiter, it’s going to help us better understand the universe around us and our place in it.”