THIS DAY IN SPACE

Discovery of GJ 581e, a Super-Earth
On March 11, 2008, astronomers using the HARPS spectrograph at the La Silla Observatory in Chile discovered GJ 581e, one of the earliest confirmed Super-Earths. Orbiting the red dwarf star Gliese 581, this exoplanet was part of a growing family of potentially habitable planets in the system, sparking early hopes of finding life beyond our solar system. GJ 581e had a mass just under twice that of Earth and completed an orbit in a mere 3.15 days. Despite its proximity to its host star—making it far too hot to support Earth-like life—it helped prove the capability of astronomers to detect low-mass exoplanets with increasing precision. The discovery was a major step in exoplanetary science, highlighting how the radial velocity method could reveal small, rocky worlds around dim stars. GJ 581e became an object of great interest in subsequent years, as scientists explored planetary system dynamics and habitability conditions beyond our own planet.

MESSENGER Prepares for Mercury Orbit
On March 11, 2011, NASA’s MESSENGER spacecraft made its final approach before entering orbit around Mercury, becoming the first mission to do so. Launched in 2004, MESSENGER had already performed multiple flybys of Earth, Venus, and Mercury itself. This date marked a crucial transition as it prepared for orbit insertion scheduled for March 18. The spacecraft was equipped with seven science instruments designed to map Mercury’s surface, study its magnetic field, exosphere, and geological history. In the days leading up to orbital insertion, MESSENGER performed crucial trajectory correction maneuvers and system checks to ensure successful capture by Mercury’s gravity. The significance of this approach lay in its potential to unlock the secrets of the innermost planet—such as its unusually high density and magnetic field. MESSENGER would go on to transmit more than 100,000 images and reveal phenomena like water ice in permanently shadowed craters at the poles. This final approach was the culmination of nearly seven years of flight and represented a landmark moment in planetary exploration.