NASA scientists find icy water on the most unexpected planet beyond the Earth, with the hottest temperatures

Time of India

20-05-2025

The search for water beyond Earth has always been an interesting area for scientists, driven by a simple yet important idea that where there is water, there may be life. The universe is filled with clues waiting to be uncovered, be it dry Martian riverbeds or icy moons orbiting gas planets.
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With the advancement in technology and every discovery, we're reminded that our solar system holds more surprises than we ever imagined.
While Mars is often the most commonly discussed planet with water beyond the Earth, in 2012, NASA scientists discovered strong evidence of water ice on the most unexpected planet with one of the most extreme environments in the solar system.
The most unlikely planet for water ice
Finding water in the solar system usually involves looking for hospitable environments, places with mild temperatures, underground water reservoirs, or atmospheres thick enough to shield and preserve moisture.
But this time it has been found on Mercury, which defies all these expectations. With an atmosphere so thin that it's barely there, a scorching surface, and a day that lasts nearly six Earth months, it seems like the last place water could survive.
Yet, during NASA's MESSENGER mission in 2012, scientists detected areas on Mercury that were not only cold but permanently shielded from sunlight. These polar regions, inside deep craters, showed something unusual, which included strong radar reflections that were highly suggestive of ice.
'The radar signatures show high reflectivity and strong depolarization,' NASA reported, which were the classic signs of water ice on planetary surfaces.
How was this discovery made?
The discovery was made without setting foot on Mercury by using instruments like the Arecibo radio telescope, the Goldstone antenna, and the Very Large Array (VLA); researchers studied radio signals bouncing off Mercury's surface. The high reflectivity and depolarization effects, especially near the poles, were strong indicators of water ice, despite the hostile surroundings.
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Why does ice stay frozen on a planet so close to the Sun?
Well, that is all about geography; the craters on Mercury's poles never see sunlight. Without exposure to heat, temperatures in these shadows remain cold enough for ice to persist for possibly billions of years.
But how did ice get there? NASA offers two possible theories. One is that water was delivered via meteorites and comets, especially during the chaotic early years of the solar system. The second is that Mercury may have once released water vapor from within, which later froze in the cold, shadowy craters.
This discovery significantly changed how scientists view planetary water sources. It proves that temperature and atmosphere aren't the only deciding factors; specific geological and orbital conditions matter, too.