Planetary Exploration

New Horizons: Possible Clouds on Pluto, Next Target is Reddish

Pluto's present, hazy atmosphere is almost entirely free of clouds, though scientists from NASA's New Horizons mission have identified some cloud candidates after examining images taken by the New Horizons Long Range Reconnaissance Imager and Multispectral Visible Imaging Camera, during the spacecraft's July 2015 flight through the Pluto system. All are low-lying, isolated small features-no broad cloud decks or fields - and while none of the features can be confirmed with stereo imaging, scientists say they are suggestive of possible, rare condensation clouds. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The next target for NASA’s New Horizons mission -- which made a historic flight past Pluto in July 2015 -- apparently bears a colorful resemblance to its famous, main destination.

Hubble Space Telescope data suggests that 2014 MU69, a small Kuiper Belt object (KBO) about a billion miles (1.6 billion kilometers) beyond Pluto, is as red, if not redder, than Pluto. This is the first hint at the surface properties of the far flung object that New Horizons will survey on Jan. 1, 2019.

Mission scientists are discussing this and other Pluto and Kuiper Belt findings this week at the American Astronomical Society Division for Planetary Sciences (DPS) and European Planetary Science Congress (EPSC) in Pasadena, California.

“We’re excited about the exploration ahead for New Horizons, and also about what we are still discovering from Pluto flyby data,” said Alan Stern, principal investigator from Southwest Research Institute in Boulder, Colorado. “Now, with our spacecraft transmitting the last of its data from last summer’s flight through the Pluto system, we know that the next great exploration of Pluto will require another mission to be sent there.”

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MOUNTAIN VIEW – NASA’s OSIRIS-REx spacecraft is slated to launch from Cape Canaveral on Thursday, September 8th. Its mission is to rendezvous with asteroid Bennu in 2018, take a sample from its surface, and return that sample to Earth in 2023.


Why are scientists so interested in this ancient lump of rock? First, Bennu is one of the darkest objects in the Solar System, suggesting it is rich in organic materials that might have seeded Earth with the starting blocks of life. We cannot find these materials today, because the organic compounds that first fell to Earth have long since disappeared – processed and endlessly recycled by geology and biology. On Bennu however, these mysterious compounds have been almost perfectly preserved. Bennu is a veritable museum in space that has been waiting 4.5 billion years to open its doors to Earth’s scientists.

John Marshall, a mission co-investigator at the SETI Institute, is eagerly awaiting the opportunity to test his ideas regarding Bennu’s topography.

“We’ve developed a mathematical model of how material might move around on the surface as a result of asteroid spinning forces,” Marshall says. “It predicts where all the ‘lumps and bumps’ will be, and how all the loose boulders and gravel are distributed. Within minutes of receiving our first close-up images during the asteroid encounter, we will know if we got it right or not.”

Scientists are also interested in the so-called Yarkovsky effect. This is a process whereby solar radiation gently nudges the asteroid, subtly changing its orbit. By being up-close with Bennu, we can better understand how surface properties affect this process. Combined with understanding material properties, this enables us to better predict if and when this asteroid might impact Earth in the 22nd century. It is a potentially dangerous lump of rock, already on our watch list.

“We will be making maps of topography, gravity variations, boulder distributions, surface composition and physical properties,” notes Marshall. “My role will be integrating spacecraft observations for the production of a global geology map. 

After we get the return samples, I will be examining small grains of the material with a scanning electron microscope to interpret their physical history. I also analyzed grains brought back from asteroid Itokawa by the Japanese Hayabusa mission. They were immensely surprising and not at all what you might have expected. I suspect (and hope) that Bennu will be equally awesome.”

“We’re proud to be part of the OSIRIS-REx, science team, through John’s work” says SETI Institute CEO, Bill Diamond. “To improve our understanding of possible sources of Earth’s biology, while simultaneously gaining insights critical to planetary defense, is a rare and exciting opportunity.”

OSIRIS-REx looks back 4.5 billion years to the origin of life, but also looks forward 100 years to help ensure the safety of life on Earth.

Marshall remarks that “I’ve made a living out of playing in the dirt – so why stop now?”


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