NASA’s astronauts may be stuck in low Earth orbit for the time being, but robotic space probes sent deep into the solar system continue to open up strange, new worlds to human scrutiny. Thursday, the space agency revealed an image sent back by the New Horizons of what appears to be a remnant of a liquid nitrogen lake. On the same day, Cassini revealed the tallest mountain on Saturn’s moon Titan.
The discovery of a frozen nitrogen lake on Pluto, nestled in the mountains near the Sputnik Planum, suggests that, at one time. Pluto was warmer and with a higher atmospheric pressure than it enjoys now. But, over millions or even billions of years, the former ninth planet from the sun cooled and leached away the atmosphere, causing the flowing liquid nitrogen to permanently freeze.
In the meantime, Cassini has returned the image of the highest peak on Titan, located in a trio of ridges called Mithrum Montes, towering at almost 11,000 feet near the moon’s equator. The mountain range was formed on Titan in ways that mountains on Earth are formed, but with a twist, suggests Jani Radebaugh, a Cassini radar team associate at Brigham Young University.
‘Mountains and cliffs on Earth usually are found in locations where forces have shoved the surface upward from underneath. Forces of erosion, including wind, rain and runoff, slowly wear them down over time. The Himalaya and Andes Mountains are examples of places where interior forces are at work today. The Appalachian Mountains represent much more ancient activity that produced similarly gigantic peaks long ago, which have since eroded.
“Cassini has found that Titan also has rain and rivers that erode its landscape. According to Radebaugh, the process probably proceeds much more slowly on Titan than on Earth because, at 10 times Earth’s distance from the sun, there is less energy to power erosive processes in the moon’s atmosphere.
“Titan’s icy crust sits atop a deep ocean of liquid water that probably acts much like Earth’s upper mantle — the layer of hot, high-pressure rock below the crust that can slowly flow and deform over time. Once a period of mountain-building ends, these fluid layers (Earth’s upper mantle and Titan’s liquid ocean) allow the crust to relax, like a person settling into a waterbed. Also, at great depth, the water-ice bedrock of Titan is softer than rock on Earth. Because of these characteristics, scientists didn’t expect mountains on Titan would tower quite as high as those on Earth, which can rise to more than 5 miles (nearly 9 kilometers) tall.
“The fact that Titan has significant mountains at all suggests that some active tectonic forces could be affecting the surface, for example, related to Titan’s rotation, tidal forces from Saturn or cooling of the crust. The next step for the researchers will be trying to figure out what could produce such tall peaks on an icy ocean world.”
The mountains of Tiran were imaged using a radar instrument on the Cassini that penetrated the smoggy atmosphere of the moon of Saturn to reveal its varied landscape.