Astronomers have been fascinated with Pluto's big heart-shaped feature since NASA's New Horizons mission photographed it in 2015.
Researchers believe they have solved the dwarf planet's heart conundrum, which may provide fresh information about its beginnings.
The feature is named Tombaugh Regio after 1930 Pluto discoverer Clyde Tombaugh. The heart is not one element, say scientists.
Tombaugh Regio's elevation, geological composition, shape, and extremely reflective surface, which is brighter white than Pluto, have eluded scientists for decades.
Pluto’s nitrogen ice lies mostly in Sputnik Planitia, the heart’s “left lobe”. The basin encompasses 745 miles by 1,242 miles (1,200 kilometers by 2,000 kilometers),
or 25% of the US, although it's 1.9 to 2.5 miles (3 to 4 kilometers) lower in elevation than most of the earth. Nitrogen ice covers the right side of the heart, but it's thinner.
An multinational team of scientists found that a cataclysmic event produced the heart using Sputnik Planitia data.
A planetary body around 435 miles (700 kilometers) in diameter, or twice the size of Switzerland from east to west, likely collided with Pluto early in its history, according to numerical calculations.