Mercury's Water Discovery, Revealed on August 23, 1991
In August 1991, a groundbreaking discovery was made about our solar system's smallest planet, Mercury. Scientists from CalTech and the Jet Propulsion Laboratory, using the Goldstone Deep Space Communications Complex's 70-meter antenna and the Very Large Array, targeted Mercury's unmapped regions in a bid to produce a radar map of the planet's hidden areas.
The radar image received by the Very Large Array on the 23rd of August was unexpectedly revealing. It showed reflective material at Mercury's north pole, reminiscent of the polar caps on Mars. This discovery was a surprise given the planet's proximity to the Sun and high average surface temperature.
The presence of such reflective material suggested the possible presence of water ice. And indeed, in 2012, NASA's MESSENGER spacecraft confirmed the presence of water ice at Mercury's north pole.
Mercury, with an average temperature of 333 degrees Fahrenheit (167 degrees Celsius) and a maximum of 800 F (430 C), might seem an unlikely candidate for ice. However, some craters on the planet rest in deep enough shadows for ice to survive. In the polar regions, the Sun barely rises, allowing temperatures in those craters to be as low as -235 F (-148 C).
The radar observations in 1991 were aimed at filling the gaps left by Mariner 10's flybys, which had only managed to photograph a small portion of Mercury's surface. The scientists conducting these observations included Gordon H. Pettengill and R. Stephen Hudson.
The discovery of water ice at Mercury's north pole was a significant development in our understanding of the solar system. It challenges our preconceived notions about the planet and opens up new avenues for research and exploration.
