A NASA space probe is beginning a long-awaited encounter with distant Pluto—and has spotted a strange heart-shaped feature on the surface. 

The former planet, which was only discovered in 1930, is so remote that no detailed views have ever been had of its surface. The best was a fuzzy view using the Hubble Space Telescope, which orbits the Earth.

But now the unmanned New Horizons spacecraft is nearing the climax of its nine-year, three-billion mile race to make the first ever visit to Pluto. NASA has declared its flyby sequence of science observations to be officially under way.

New Horizons will be closest to Pluto and its family of five moons, in just under a week, on July 14. But already, speeding at 36,373 mph—100 times faster than an airliner—the probe is capturing images that show clear surface detail.

The latest was taken on Tuesday, July 7, from a distance of just under five million miles. Closest approach will bring it to a distance of about 7,750 miles.

One dark feature has been dubbed “the whale”. And a large brighter zone, about 1,200 miles wide, resembles a heart in the latest picture. Scientists believe it may be covered with a frost of frozen methane, nitrogen, or carbon monoxide.

Earlier, NASA released a crude map of Pluto created from images taken between June 27 and July 3 by New Horizons’ Long Range Reconnaissance Imager (LORRI) combined with lower-resolution color data from the spacecraft’s Ralph instrument. The map is centred on the side of Pluto that will be on view close-up during the flyby on July 14.

A leading UK Pluto expert is Dr Jane Greaves, of the University of St Andrews in Scotland. She told me today: “It is really exciting now that we are getting really close to Pluto and getting the pictures. It’s in our headlights now.

“Just seeing the terrain close-up will tell us a lot about how it formed, and its history. We know the colours of the rocks, from changes in its light as it rotates, but actually seeing why those colours are there will be really important.

“Pluto’s very thin atmosphere basically comes from the ice on the surface boiling off, so just seeing that in action as the spacecraft flies past will be pretty amazing. Some of the ice is methane, a lot of it is nitrogen, and there’s carbon monoxide. All these things that would be pretty nasty if you transferred them into the atmosphere of the Earth in large quantities.”

When New Horizons gets closest to Pluto, it will see features in 500 times greater detail. Then the probe will race away out into a region of the Solar System, filled with mysterious icy objects, that is called the Kuiper Belt.

Pluto was discovered by Clyde Tombaugh in 1930 from the Lowell Observatory in Arizona, and its name was suggested by an 11-year-old British schoolgirl, Venetia Burney. In 2006, just seven months after New Horizons was launched, the International Astronomical Union demoted it from the premiere league of planets to a new status of dwarf planet.