Despite initial guesses that Pluto may be similar to Neptune’s Triton satellite, early information from NASA’s New Horizons showed that Pluto is actually another object.
The Triton map released last year shows the satellite in its smallest details. The map is based on data from the Voyager 2 spacecraft when the spacecraft flew past the satellite in 1989, as part of a larger tour of the solar system.
Under the guidance of Paul Schenk from the Institute of the Moon and the Planets in Houston, the map was made based on a comparison of Triton with Pluto. Both bodies are formed in the outer Solar System, and this suggests that they may have some similarities.
“But as new high-resolution data from New Horizons slowly overcoming its path in the solar system is received, it is surprising how insignificant these similarities are,” said Schenk. “Even the smallest features are very different in these two bodies.”
Image of Triton, satellite of Neptune in high resolution. The large black area on the left is missing information. “The main conclusion is that there cannot be two identical bodies in this part of the Solar system or they cannot have the same geological history,” said Schenk.
Scientists had to get evidence of differences, to be sure. Triton is a fugitive from the outer part of the solar system, long captured by Neptune. The strength of this gravitational field has melted vast plains on the surface of Triton, erasing old craters and terrain.
Pluto, meanwhile, quietly rotates in the space of the solar system over billions of years, and did not go through such a perturbation. Thus, its relief is expected to be somewhat older, rockier, and with many craters.
“But there are secrets that go beyond their various geological histories,” said Schenk. “The youngest terrain on Pluto (Satellite Planum) is significantly different from the youngest terrain on Triton. And there are mountains on Pluto, whose existence on a cold dwarf planet is difficult to explain. ”
The satellite Planum is a young special area of Pluto, over which the geological history of the relief is being studied.
“In addition, on the surface of Pluto there is a huge cover of nitrogen ice; how he got there and whether such a phenomenon (placement in the same place as Pluto) can take place on Triton is an open question, ”Schenk explained. Not all data have been obtained from New Horizons yet. The spacecraft cannot quickly send images after it gets as close as possible in July (not an easy task for such a distance). “It is hoped that many images will be uploaded by the end of October,” Schenk said.
But even after that, Schenk said there will be more missions to the outer solar system to really understand its geological history. The James Webb Space Telescope, though powerful, cannot fully capture these small dwarf planets. And even if New Horizons reaches another object Kuiper Belt - an ice object of the outer solar system - it will be small, not corresponding to the size of Pluto.
Schenk added that it’s a “fair view” that at least the large Kuiper Belt objects can differ significantly from each other based on the data we have, such as color and brightness.