With tomorrow’s arrival of Valentine’s Day, love is in the air—and the sky beyond. The universe is loaded with symbols of this special day, from the flower-shaped Valentine’s Day Nebula in the constellation Cepheus, to heart-shaped craters and mesas on Mars.
But in this era when scientists using the New Horizons spacecraft have unveiled the face of Pluto, nothing in space evokes thoughts of Valentine’s Day like that icy body’s distinct heart-shaped feature.
For years, scientists detected splotches on Pluto’s surface that were brighter than surrounding areas. Former Lowell Observatory astronomer Marc Buie led efforts to create albedo maps of Pluto based on these observations, but not until New Horizons would Buie and his colleagues see detailed images of these blemishes — most notably the so-called “Heart”— and begin to decipher their extent and physical characteristics.
The Heart is located a little north of Pluto’s equator. With a diameter of almost 1,000 miles, it is easily the largest surface feature on a parent body that only measures 1,474 miles across (a feature at that scale on Earth would spread twice the width of the United States!). On July 15 of last year, a day after New Horizons made its closest approach to Pluto, members of the New Horizons team informally named it Tombaugh Regio; the first word honors Pluto discoverer Clyde Tombaugh while the second word is Latin for “region”.
Tombaugh Regio consists of lobes, each with its own distinct geology. Even in the early stages of deciphering initial observations of these regions, scientists have discovered a number of fascinating features, particularly in the western lobe, informally known as Sputnik Planum (Sputnik after Earth’s first artificial satellite, Planum the Latin word for plain).
Sputnik Planum takes up an area of about 323,000 square miles, roughly the combined size of Texas and Oklahoma. It is smoother than the eastern lobe and may have been formed by an impact that gouged out a crater, which eventually filled with nitrogen ice.
Scientists, to their surprise, have not detected any craters here, indicating a relatively young surface that suggests Pluto may be geologically active. In fact, Sputnik Planum has quickly turned into a geologist’s paradise, with areas of blocky hills, 11,000-foot-high mountains of ice, 20-mile-wide polygons, wind streaks, pits, and ice flows.
Scientists, including Lowell’s Will Grundy, head of the New Horizons Surface Composition team, still have months of data to receive from the spacecraft, and that will result in years of analysis. Who knows what further treasures they will uncover in Tombaugh Regio? If the new discoveries are anything as compelling as what’s already been revealed, space enthusiasts will no doubt continue their love for the little world with the big heart.