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In 1930, Clyde Tombaugh, a 25-year-old amateur astronomer, noticed a small, faint object in the night sky.

He worked at Lowell Observatory in Flagstaff, Arizona for about a year when he used a blinking comparator – a special kind of microscope that can examine and compare images – to see what was once believed to be the ninth planet. in our solar system: Pluto.

By all accounts, Pluto was … well … strange. At some point, astronomers believed that it could potentially be larger than Mars (it is not). Its unusual 248-year orbit is known to cross the path of Neptune. Today Pluto is recognized as the largest object in the Kuiper belt, but is no longer considered a planet.

In 2006, the International Astronomical Union voted to downgrade Pluto, defining the planet as a body orbiting the sun, circular in shape and “clearing out the surroundings around its orbit” – which means that it has become dominant in terms of gravity, so there is the orbital zone has no bodies other than its own satellites. Since Pluto did not check this third box, it was considered a dwarf planet.

Now, a new concept mission, unveiled by NASA, aims to take a close look at Pluto and its nearby systems. Proposed in late 2020, Persephone will investigate whether Pluto has an ocean and how the planet’s surface and atmosphere evolved.

Persephone will send a spacecraft armed with high-definition cameras into orbit around Pluto for three years and will map its surface as well as the surface of its largest moon, Charon.

But why is Pluto worth visiting?

In the same year that Pluto was thrown off its planetary pedestal, NASA sent a New Horizons mission to Pluto and the Kuiper belt to better understand the outer edge of our solar system.

Reaching Pluto in 2015, New Horizons has become a scientific treasure. A close-up of Pluto showed potentially active mountain ranges, ices, and amazing records of geological history on its surface.

Carly Howett, planetary physicist and principal investigator for Persephone, says New Horizons showed us just how complex this part of the cosmos really is.

“It’s not that New Horizons basically had new technologies, but it kind of gave people an idea of ​​what Pluto’s system might look like,” Howett says. “The world saw Pluto for the first time.”