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Strange fractures seen on Pluto’s surface; study considers feasibility of orbiter

New Horizons Pluto flyby

Artist’s rendition of New Horizons’ flyby of Pluto and its moon Charon. Image Credit: NASA/JHU-APL/SwRI

Yet another strange feature appears on Pluto’s surface in the latest New Horizons data sent back to Earth, as several fractures that converge at a central point result in an image resembling a giant spider.

A close up of the feature (below), located northeast of Sputnik Planum, shows six extensional fractures (highlighted in the annotated image by mission team members with white arrows) all meeting at a central point.

The longer fractures are aligned north to south, whereas a shorter one is aligned east to west. Sleipnir Fossa, the longest fracture, extends 360 miles (580 km). In contrast, the shortest, horizontal fracture has a length of 60 miles (100 km).

Underneath the fractures, which make up the “legs” of the “spider”, reddish deposits are exposed.

The unusual feature cuts through Pluto’s “snakeskin terrain“, informally named Tartarus Dorsa, to the south, while bordering higher latitude rolling plains to the north and west.

The Icy ‘Spider’ on Pluto

The Icy ‘Spider’ on Pluto. This feature consists of at least six extensional fractures (indicated by white arrows in this annotated version) converging to a point near the center. The longest fractures are aligned roughly north-south, and the longest of all, the informally named Sleipnir Fossa, is more than 360 miles (580 kilometers) long. The fracture aligned east-west is shorter and reaches less than 60 miles (100 kilometers) long. To the north and west, the fractures extend across the mottled, rolling plains of the high northern latitudes, and to the south, they intercept and cut through the bladed terrain informally named Tartarus Dorsa. Image & Caption Credit: NASA/JHU-APL/SwRI

New Horizons’ Ralph / Multispectral Visible Imaging Camera (MVIC) captured this image about 45 minutes before closest approach on July 14, 2015, from a distance of approximately 21,100 miles (33,900 km), at a resolution of about 2,230 feet (680 meters) per pixel.

Mission geology team member Oliver White emphasized that the pattern does not look like anything that is seen on any world in the outer Solar System, though it bears some resemblance to features on Mercury and Venus.

NASA’s MESSENGER orbiter found troughs somewhat similar on Mercury in a region dubbed the Pantheon Fossae formation.

Radially-centered fractures known as “novae“, which also bear some similarity to those on Pluto, were seen on Venus by NASA’s Magellan spacecraft.

Parallel-running fractures in long belts have also been seen elsewhere on Pluto (shown below), and mission scientists think they are caused by “global scale extension of Pluto’s water-ice crust”.

“Oh, what a tangled web Pluto’s geology weaves,” Oliver said. “The pattern these fractures form is like nothing we’ve seen in the outer Solar System, and shows once again that anywhere we look on Pluto, we see something different.”

Fracture feature on Pluto in 3-D

Fracture feature on Pluto in 3-D. Image Credit: NASA/JHU-APL/SwRI

Like Pluto’s other complicated surface features, the “spider” pattern is a sign the world is geologically active. Mission scientists think the point where the fractures converge is experiencing stress caused by material welling up from beneath the surface, creating the unusual, radiating pattern.

As part of New Horizons’ continuous public outreach, mission research scientist Ross Beyer, a planetary scientist with the Carl Sagan Center at the SETI Institute and at the NASA Ames Research Center in California, discussed the process of mapping the planet from mission images in an April 1 blog entry.

Celebration of the flyby and data obtained from it were a central theme of the 2016 Northeast Astronomy Forum, held at SUNY Rockland Community College in Suffern, NY, on April 9–10.

New Horizons Principal Investigator Alan Stern, the event’s keynote speaker, discussed the mission’s history and Pluto findings, while Annette Tombaugh-Sitze and Alden Tombaugh, the daughter and son of the late Pluto discoverer Clyde Tombaugh, reminisced about their father’s life and career.

Other Pluto-themed talks were presented by New Horizons Mission Operations Manager Alice Bowman, Gerard van Belle of Lowell Observatory, Lowell Observatory historian Kevin Schindler, and Lowell Observatory trustee William Lowell Putnam IV, great-grandnephew of founder Percival Lowell.

“What a beautiful little planet we went to explore, and in a complicated place,” Stern said to a packed auditorium.

A total of 458 newspapers headlined the flyby on July 15, 2015, the day after closest approach, on all seven continents, he added. People worldwide were fascinated by Pluto and its moons.

A composite of enhanced color images highlights the striking differences between Pluto and Charon.

A composite of enhanced color images highlights the striking differences between Pluto (lower right) and Charon (upper left). Image Credit: NASA/JHU-APL/SwRI

Pluto and Charon have been orbiting together as a binary system for four billion years, yet they don’t look anything alike, he stressed. “Imagine how diverse the planets of the Kuiper Belt will be when we’ve explored them all.”

Many mission scientists expected the spacecraft to find additional satellites beyond Charon and the system’s four known small moons and were surprised when none were located, Stern said.

Because Pluto was found to be so complex and diverse, questions have already been raised by both scientists and members of the public about a possible return to Pluto, this time with an orbiter.

Such a mission is already feasible with current technology, Stern stated. NASA’s new Space Launch System, currently under development, will be the most powerful rocket to ever be built, and along with ion propulsion, could propel a spacecraft to Pluto either as fast or even faster than New Horizons traveled.

Electric propulsion could be used to slow down the spacecraft and enter it into Pluto orbit. “We’re ready to do that mission if the scientific community wants to do it,” he said.

On Monday, April 11, Princeton Satellite Systems, Inc., a small company specializing in aerospace control, released a statement saying they are studying a potential Pluto orbiter and lander mission using its Direct Fusion Drive (DFD) concept.

Based on the fusion reactor being developed at the Princeton Plasma Physics Laboratory, DFD “provides high thrust to allow for reasonable transit times to Pluto while delivering substantial mass to orbit: 1,000 kg delivered in four to six years.”

Phase I of the study will examine new engine models for the potential spacecraft.


Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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