THIS DAY IN SPACE

Launch of STS-84 to Mir Space Station
On May 20, 1997, Space Shuttle Atlantis launched on mission STS-84 to dock with Russia’s Mir space station. This marked the sixth docking between a U.S. Space Shuttle and the Mir station under the Shuttle-Mir program, a precursor to the International Space Station (ISS). The mission exemplified the growing cooperation between the United States and Russia in post-Cold War space exploration. STS-84 carried supplies, experiments, and astronaut Mike Foale, who replaced Jerry Linenger aboard Mir. This collaborative spirit laid the foundation for joint missions aboard the ISS and demonstrated the operational logistics of international space living. The success of STS-84 strengthened engineering protocols for orbital docking and highlighted the importance of redundancy and cross-training for astronauts of different nations — now standard practice aboard the ISS. The mission also involved several experiments related to human adaptation to microgravity and biological studies that would inform long-duration spaceflight planning.

Discovery of LHS 1140b: Potentially Habitable Super-Earth
On May 20, 2015, astronomers identified LHS 1140b, a rocky exoplanet orbiting a red dwarf star about 40 light-years from Earth. Its size (about 1.4 times Earth’s radius) and its placement within the star’s habitable zone — where liquid water could exist — made it one of the most promising Earth-like planets at the time. The planet was discovered using the transit method, where periodic dimming of the star’s light indicated a planet passing in front of it. Follow-up radial velocity studies confirmed its mass and density, suggesting a solid, rocky composition. LHS 1140b’s slow rotation and thick atmosphere (suspected but not yet confirmed) fueled hypotheses about its ability to maintain surface water. The discovery of such a potentially habitable world around a relatively quiet red dwarf further energized the scientific community’s search for biosignatures and advanced telescopes capable of atmospheric analysis. This planet remains a prime target for future missions aiming to detect alien life.