New Horizons mission extension submitted to NASA; images of Pluto’s hazes show new detail

Laurel Kornfeld

Artist’s impression of NASA’s New Horizons spacecraft encountering a Kuiper Belt Object (KBO). Image Credit: NASA/JHU-APL/SwRI/Alex Parker

As NASA’s New Horizons spacecraft reached the halfway mark in sending back data from last July’s Pluto flyby, members of the mission team formally submitted an extended mission proposal to NASA outlining a close flyby of a small Kuiper Belt Object (KBO) on New Year’s Day 2019 and other observations in the outer Solar System.

Dubbed the Kuiper Extended Mission (KEM), the proposal seeks funding for a flyby of KBO 2014 MU 69 followed by distant observations of around 20 KBOs and subsequent astrophysical cruise science.

MU 69 , discovered via the Hubble Space Telescope in 2014, has a diameter between 21 and 40 km and is located about a billion miles beyond Pluto.

It is 1,000 times more massive than Comet 67P/Churyumov-Gerasimenko, currently orbited by the Rosetta spacecraft, but 500,000 times less massive than Pluto, putting it into an intermediate category between comets and small planets.

The KBO has spent four billion years essentially unchanged in the cold reaches of the outer Solar System, making it the most pristine object ever visited by a spacecraft and an ideal object for scientists seeking to better understand planetary accretion.

New Horizons will fly four times closer to MU 69 than it did to Pluto, coming within 1,900 miles (3,000 km) of its surface. All seven science instruments will be used to study it, resulting in high-resolution imaging, detailed global high-resolution mapping in color, the study of surface properties, compositional mapping, spectroscopy, as well as searches for an atmosphere, moons, and rings.

The data will then be sent back to Earth over a period of 20 months.

If the proposal is approved and funded, flyby operations will begin about 100 days in advance of the encounter, in late September 2018, and will continue for a week after the flyby.

Although only MU 69 will be studied up close, the proposal includes a list of 20 other KBOs that will be observed from a distance between 2016 and 2020, among them dwarf planets Haumea, Makemake, and Eris.

Ixion and Quaoar, also suspected to be large enough to qualify as dwarf planets, are on the observation list as well.

The spacecraft will study the shapes and surface properties of all these objects and also search for satellites and rings.

In addition to studying individual KBOs, New Horizons will also measure dust, plasma, and neutral gas in the space environment through 2021, when the spacecraft reaches a distance of 50 Astronomical Units (AU; one AU equals the average Earth-Sun distance of 150 million kilometers or 93 million miles) from the Sun.

As with all mission extension proposals, NASA will peer review this one and convey its decision to the mission team in June or July.

Meanwhile, stunning new images of Pluto provide insight into the structure and behavior of its layered nitrogen atmosphere.

They show that while the atmosphere’s haze keeps its overall vertical structure, individual haze layers vary in brightness, which scientists attribute to the phenomenon of buoyancy waves.

Buoyancy waves are also known as gravity waves, but they are different from the cosmic gravity waves first detected in February of this year. The latter are ripples in the fabric of spacetime while those in Pluto’s atmosphere are caused by wind flowing over mountain ranges.

The only other worlds known to experience buoyancy waves are Earth and Mars.

This latest image of Pluto’s haze layers was taken on July 14, 2015, as New Horizons departed from the Pluto system. The Long Range Reconnaissance Imager (LORRI) photographed haze layers above particular regions on Pluto several times at intervals ranging from two to five hours.

During that time, the brightness of individual haze layers changed by up to 30 percent, but the layers’ height remained constant.

“Pluto is simply amazing. When I first saw these images and the haze structures that they reveal, I knew we had a new clue to the nature of Pluto’s hazes. The fact that we don’t see the haze layers moving up or down will be important to future modelling efforts,” noted Andy Cheng of the Johns Hopkins University Applied Physics Lab and LORRI principal investigator.

Oliver White, New Horizons postdoctoral researcher in planetary science based at California’s NASA Ames Research Center, describes the process of creating a geological map of Pluto in his April 15 blog, “Mapping to Make Sense of Pluto“.

Geological maps help scientists create a chronology for the surfaces of objects like Pluto, enabling them to tease out the processes that created and changed each type of terrain and the time periods when the processes occurred.

In creating the geological map, White notes he relied heavily on data taken by the Ralph/Multispectral Visible Imaging Camera (MVIC) and by the Linear Etalon Imaging Spectral Array (LEISA).