Dunes on Pluto? It’s possible
New Horizons photographs paint a diverse landscape unanticipated by scientists
CAPE CANAVERAL, FLA.— The spigot has opened again, and Pluto pictures are pouring in once more from NASA’s New Horizons spacecraft.
These newest snapshots reveal an even more diverse landscape than scientists imagined as New Horizons swept past Pluto in July, becoming the first spacecraft to visit the distant dwarf planet.
“If an artist had painted this Pluto before our flyby, I probably would have called it over the top — but that’s what is actually there,” said Alan Stern, New Horizons’ principal scientist from Southwest Research Institute in Boulder, Colo.
In one picture, ancient craters border much younger icy plains. Also visible are dark ridges that some scientists speculate might be dunes.
One outer solar-system geologist, William McKinnon of Washington University in St. Louis, said if the ridges are in fact dunes, which would be “completely wild” given Pluto’s thin atmosphere.
Dunes are undulating ridges of particles piled up by blowing wind, but the air of present-day Pluto is much too thin and weak to sculpt the fields of dunes, some of which stretch for kilometres. That could suggest that Pluto once possessed a much thicker atmosphere. If they are not dunes, then some force other than wind created them.
“It’s a head-scratcher,” McKinnon said in a written statement.
It is also unknown whether the dune-like structures are made of ice particles or san- dlike bits of rock. Some of the structures are fairly bright, reflective as ice might be; others are very dark.
“The dunes may all be identical in composition,” Stern said, “but some may have a veneer of dark stuff on them. Or they may be different. We just don’t know.”
Scientists started getting fresh Pluto pictures last weekend, after several weeks of collecting engineering data from New Horizons. The latest images were published Thursday.
Besides geologic features, the images show that the atmospheric haze surrounding Pluto has multiple layers. What’s more, the haze creates a twilight effect that enables New Horizons to study places on the planet’s night side that scientists never expected to see. Monday marks two months from New Horizons’ close encounter with Pluto on July 14, following a journey from Cape Canaveral, Fla., spanning 4.8 billion kilometres and 91⁄ years.
2 As of Friday, the spacecraft was 71 million kilometres past Pluto.
So much data was collected during the flyby it will take until next fall to retrieve it all on Earth.
New Horizons’ next target, pending formal approval by NASA, will be a much smaller object that orbits 1.6 billion kilometres beyond Pluto. It, too, lies in the so-called Kuiper Belt, a frigid twilight zone on the outskirts of our solar system. Following a set of manoeuvres, New Horizons would reach PT1 — short for Potential Target 1 — in 2019. With files from the New York Times
“If an artist had painted this Pluto before our flyby, I probably would have called it over the top — but that’s what is actually there.”
ALAN STERN NEW HORIZONS SCIENTIST