New Evidence Suggests Pluto Started Hot and Contained an Ocean

mysteries about the distant dwarf planet continue to unfold

By Jonny Lupsha, Wondrium Staff Writer

The formerly designated planet Pluto may have once looked far different than it does today, CNN reported. Now a frozen planet that reaches nearly -400 degrees Fahrenheit, the celestial body may have once been hot and played host to bodies of water. Our knowledge of Pluto is still limited.

Pluto with moon
Launched in January 2006, the New Horizons spacecraft went into programmed hibernation for more than seven years after getting a gravity assist from Jupiter, accelerating its journey to Pluto. It wasn’t until July 15, 2015, that scientists began to receive data about Pluto. Photo by Vadim Sadovski / Shutterstock

According to CNN, the Pluto we know today may not represent its original environment. “Using geologic observations of Pluto’s surface, new research suggests that Pluto actually started out in a hot formation scenario,” the article said. “Researchers modeled and compared hot versus cold formation scenarios and found that the surface features on Pluto best match hot. In that scenario, the liquid ocean would slowly freeze over time, although not completely, and cause the extensional faults seen in Pluto’s icy crust.”

This drastic change in Pluto’s environment serves as just another example of how far we have to go in learning about the planet itself.

Finding Pluto

What we do know about Pluto stems partly from how recently it was discovered.

“Pluto was discovered in 1930 by Clyde Tombaugh,” said Dr. Sabine Stanley, Bloomberg Distinguished Professor in the Morton K. Blaustein Department of Earth and Planetary Sciences at Johns Hopkins University. “He painstakingly spent many nights at the telescope, looking at photographic plates where images from telescopes were stored.”

Dr. Stanley said that Pluto’s diameter is under 2,400 kilometres. That means it’s smaller than seven of the moons in our solar system, including Neptune’s moon Triton and Earth’s moon. In fact, it’s 55% smaller than Jupiter’s moon Ganymede, which is the largest moon in our solar system.

“In horizontal extent, Pluto is comparable to about half the continental United States,” she said. “Pluto’s average density is about 1,900 kilograms per cubic meter. This tells us that Pluto is a mixture of ice and rock, much less dense than our Moon, and slightly less dense than Triton or Ganymede.”

New Horizons Mission

Dr. Stanley said that due to Pluto’s elliptical orbit around the Sun, it’s often much further away from Earth than it is at other times. This makes it far more difficult to reach and to study. Additionally, scientists believe Pluto’s atmosphere may change due to its distance from the Sun, and they wanted to be able to study it while it was at its nearest distance and maximum effect from solar heating. To do this, they devised the New Horizons mission.

“The New Horizons spacecraft was launched in January of 2006,” she said. “At the time, its launch speed of 10 miles per second—that’s over 36,000 miles per hour—made it the fastest spacecraft ever launched. About 13 months after launch, the spacecraft flew by Jupiter to get a gravity assist, which sped up the spacecraft to around 50,000 miles per hour.

“That boost knocked three years off New Horizon‘s flight time to Pluto.”

According to Dr. Stanley, after the Jupiter flyby, the New Horizons spacecraft entered a state of programmed hibernation for more than seven years. It wasn’t until July 15, 2015, that scientists began to receive data from the spacecraft just outside Pluto. Due to the distance between the spacecraft and Earth, it took 15 months to receive all six gigabytes of data it had captured. However, it was worth the wait. New Horizons brought us priceless insight into the dwarf planet that we could only dream of previously.

Due to Pluto’s distance from us, studying it is very tedious work. However, thanks to missions like New Horizons, we continue to learn fascinating information about it.

Dr. Sabine Stanley, Ph.D., contributed to this article. Dr. Stanley is a Bloomberg Distinguished Professor in the Morton K. Blaustein Department of Earth and Planetary Sciences at Johns Hopkins University. She received a HBSc degree in Physics and Astronomy from the University of Toronto and then completed M.A. and Ph.D. degrees in Geophysics from Harvard University.