Suddenly the tenth rock from the sun – the farthest planet in our solar system - has been brought up close and personal by a robotic explorer called New Horizons. And are scientists surprised! The spectacular images of icy mountains—some as tall as the highest peaks in the Himalayas— and iced up pools of water sent back by the New Horizons spacecraft are so different from the barren rock that Pluto was once thought to be. In fact, NASA’s dramatic announcement about blue skies and icy patches on Pluto’s surface may just be the tip of the iceberg, as planetary scientists will take years to crunch the New Horizons’ data.
The average Plutonian surface temperature is minus 235 Celsius, which makes the planet’s surface so cold that gases like nitrogen, methane, and carbon dioxide freeze solid, resulting in a surreal landscape. At such extreme temperatures, water becomes stony. Pluto’s interior though seems to be warmer, and scientists are excited over the possibility of finding an ocean deep in the planet’s core. In fact, the latest findings point to a dynamic chemistry happening on Pluto’s surface which is apparently interacting with its tenuous atmosphere. There is enough heat generated by the chemical reactions to allow for an ocean of water to exist between the planet’s rocky core and its icy outer layer. Astronomers have found similar dynamics at work on icy satellites of other planets too, like Jupiter’s Europa and Callisto.
And where there is water, it’s reasonable to assume some form of life could exist too. Pluto’s ocean, however, is unlikely to be home to any bio-organisms for the simple reason that it’s too dark and lacks sufficient sunlight, ergo energy, to power life. Never mind if you could actually read a book on Pluto during daytime: the Sun would be 300 times brighter there than the full Moon on Earth. So the only life on Pluto—if it ever existed—must have been microbial bio-organisms in the distant past when the planet’s rocky core was much hotter.
But even without the prospects of finding Plutonian life, the Solar System’s tiniest planet is still one of the most exciting places to explore, as it holds the key to some of the most important questions before humankind. Pluto’s atmosphere, for instance, is actually escaping to space—a unique phenomenon in the Solar System. The New Horizons stumbled on to this amazing fact when its instruments detected a frigid cloud of ionized gases trailing thousands of miles behind Pluto like a gigantic streamer. This ‘tail’ is Pluto’s atmosphere which is leaking into space, as it is sucked away by the solar wind (a surge of ionised particles pouring out of the Sun in all directions). It’s quite probable that infant Earth too lost its original hydrogen-helium atmosphere to space the same way.
Unlike the inner, rocky planets of the Solar System, or the outer gas giants like Jupiter, Pluto belongs to a planetary group called ‘ice dwarfs’ that graze in the Kuiper Belt—a region of space beyond Pluto and billions of miles from the Sun—that is filled with tens of thousands of icy rocks and asteroids left over from the formation of the solar system more than 4.6 billion years ago. We can learn a lot about the evolution of the Solar System by studying the Kuiper Belt, which offers a unique window for peering more than 4.6 billion years back in time—when the planets formed out of interstellar gas and dust— to ‘see’ how material interacted in the early Solar System. Exploring Pluto and beyond is a giant leap in this direction.
Prakash Chandra is a science writer. The views expressed are personal.