Why Pluto 'Is the New Mars'

The best image of Pluto, thanks to New Horizons. (Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute) Thanks to all the information pouring in from NASA’s New Horizons mission, Pluto is making a comeback. As New Horizons principle investigator Alan Stern says, “Pluto is the new Mars” – and that’s not just because of its rising popularity. The nickname, which Stern credits fellow New Horizons team member Jeff Moore with bestowing, comes in part from several intriguing similarities the distant icy world shares with the famous red planet. Both boast an array of surface and atmospheric puzzles sure to keep scientists intrigued for some time. “There are really so many ways Pluto reminds us of Mars,” says Stern.Atmospheric Decline Puzzling atmospheric questions linger over Mars and Pluto. For Mars, the questions involve how its atmosphere disappeared and what that meant for any liquid on the planet’s surface. Pluto is also losing its atmosphere, but at a far slower rate than scientists expected before New Horizons arrived. According to Stern, the atmosphere is escaping about 500 times slower than estimated before the flyby. That may come from a cooler-than-expected upper atmosphere, which slows down how much material is lost. Something in the air is keeping things chilly, but exactly what remains unknown. “We are still searching for that mystery molecule that can explain this much cooler upper atmosphere,” Stern said. A mystery molecule isn’t the only thing floating in the air. Pluto, like Mars, has a handful of tenuous clouds. On both planets, the clouds could suggest unusual weather patterns that, at least on Pluto, were unexpected.