Nearly eight years after its historic Pluto flyby, NASA’s New Horizons probe is getting ready for another round of observations made from the icy edge of the solar system — and this time, its field of view will range from Uranus and Neptune to the cosmic background far beyond our galaxy.
Scientists on the New Horizons team shared their latest discoveries, and provided a preview of what’s ahead, during this week’s Lunar and Planetary Science Conference in The Woodlands, Texas.
We previously examined how Neptune’s largest moon, Triton, could answer the longstanding question: Are we alone? With its nitrogen geysers discovered by NASA’s Voyager 2 spacecraft, possible interior ocean, and lack of craters, Triton could be geologically active, which makes it an excellent celestial body for future astrobiology missions. But Triton isn’t the only place on the edge of the solar system which garners interest for finding life beyond Earth, as one of the most familiar and well-known (former) planets also exhibits evidence of recent geological activity and crater-less surface features. This is everyone’s favorite dwarf planet, Pluto, which like Triton has only been visited by one spacecraft, this one being NASA’s New Horizons, in 2015. But even with only one visitation, we discovered so much about Pluto, and what it might be hiding, as well.
Pluto’s largest moon, Charon, started off as a beautiful, smooth red grape until someone came along, mostly peeled it, tried to smoosh it, then just gave up and walked away, leaving the poor moon to look like the absolute travesty that it is. Okay, so maybe that’s not exactly what happened, but Charon just looks like a mess and scientists want to know why. Never mind its smooshed equator, but what’s the deal with its red cap? Where did it come from and why is it red?
After New Horizons made its close flyby of Pluto in July of 2015, scientists were astounded at the incredible closeup views of Pluto’s surface. One of the most intriguing and mysterious features was a bright plain inside the prominent heart-shaped feature on Pluto, called “Tombaugh Regio” (Tombaugh Region) named after Clyde Tombaugh, who discovered Pluto in 1930.
The region is composed of a broken surface of irregularly-shaped segments that appear to be geologically young because no impact craters are part of the terrain.
As the New Horizons spacecraft hurtles out towards interstellar space, it has now reached an historical milestone. On April 17, 2021, New Horizons passed 50 astronomical units, or 50 times Earth’s distance from the Sun. It is just the 5th spacecraft to reach that distance, joining the Voyagers 1 and 2 and the Pioneers 10 and 11.
In 2017, the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) made history with the detection of a mysterious object called Oumuamua (Hawaiian for scout). Unlike countless other small objects that Pan-STARRS had detected before, Oumuamua seemed to originate from beyond the solar system. The first known interstellar object detected in the solar system, Oumuamua, with its odd trajectory, strange shape, and unusual acceleration, led to a flurry of activity in the astronomical community and an avalanche of wild claims of extraterrestrial space ships from various fringes of the media. A pair of papers published by Alan Jackson and Steven Desch of Arizona State University earlier this month reveals the best fit model for the identity of our extrasolar visitor. No, it isn’t aliens, but it’s pretty spectacular. Oumuamua seems to be a shard of a Pluto-like planet from another solar system!
We can thank NASA’s New Horizons spacecraft for opening our eyes up to Pluto’s complexity. On July 14th, 2015, the spacecraft came within 12,500 km (7,800 mi) of the dwarf planet. During the flyby, New Horizons was able to characterize Pluto’s atmosphere and its surface.
Among the things New Horizons saw was a region of snowcapped mountains.
Scientists have learned a lot about the atmospheres on various worlds in our Solar System simply from planetary sunrises or sunsets. Sunlight streaming through the haze of an atmosphere can be separated into its component colors to create spectra, just as prisms do with sunlight. From the spectra, astronomers can interpret the measurements of light to reveal the chemical makeup of an atmosphere.
It seems unlikely that an ocean could persist on a world that never gets closer than 30 astronomical units from the Sun. But that’s the case with Pluto. Evidence shows that it has a sub-surface ocean between 100 to 180 km thick, at the boundary between the core and the mantle. Other Kuiper Belt Objects may be similar.
But time might be running out for these buried oceans, which will one day turn to ice.