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New Delhi: hat looks like a simple, heart-shaped mark on Pluto’s surface has turned into one of the most iconic images in space exploration, but the story behind it is far more scientific than sentimental.

The viral image, widely shared on social media, was captured by NASA’s New Horizons spacecraft during its historic flyby of Pluto in 2015. The striking heart-shaped region, officially called Sputnik Planitia, has since become a symbol of Pluto’s surprising complexity and beauty.

Scientists from the University of Oxford, including planetary scientist Dr Carly Howett, have now shed light on how this iconic image was created and why it remains scientifically significant even a decade later. Dr Howett was part of the team behind the Ralph instrument, the powerful colour imaging system onboard New Horizons that captured Pluto in unprecedented detail.

According to researchers, the heart shape is not a coincidence or a surface stain, but a massive glacier of nitrogen ice stretching across hundreds of kilometres. The region reflects sunlight more effectively than surrounding areas, making it appear brighter and giving it its distinct shape.

What stunned scientists most was Pluto’s geological activity. Despite being a small, distant and extremely cold dwarf planet, Sputnik Planitia shows very few impact craters, indicating that the surface is relatively young, possibly less than 100 million years old. This suggests that Pluto is still evolving, challenging long-held assumptions that such distant worlds are geologically dead.

The Ralph instrument also revealed Pluto’s colourful surface composition. Red and brown patches seen across the dwarf planet are believed to be caused by tholins, complex organic molecules formed when sunlight interacts with methane in Pluto’s atmosphere. These compounds eventually settle on the surface, giving Pluto its reddish hues.

Adding to the mystery, New Horizons data also showed a thin, bluish atmospheric haze surrounding Pluto. Unlike Earth’s blue sky, Pluto’s haze is created by tiny particles that scatter sunlight, further highlighting the planet’s unexpected atmospheric complexity.

The spacecraft travelled nearly 5 billion kilometres over nine years to reach Pluto, sending back data that scientists are still analysing today. Each new insight continues to reshape how researchers understand not just Pluto, but the outer reaches of the solar system known as the Kuiper Belt.

What began as a viral image has since become a powerful reminder of why space exploration matters. Pluto’s heart is not just visually striking, it represents discovery, curiosity, and the idea that even the most distant worlds can surprise us.