Solar sails rely upon pressure exerted by sunlight on large surfaces. Get the sail closer to the sun and, not surprisingly, efficiency increases. A proposed new mission called Mercury Scout aims to take advantage of this to explore Mercury. The mission will map the Mercurian surface down to a resolution of 1 meter and, using the highly reflective sail surface to illuminate shadowed craters, could hunt for water deposits.

Unlike conventional rocket engines that require fuel which itself adds weight and subsequently requires more fuel, solar sails are far more efficient. Light falling upon the sail can propel a prob across space. It's a fascinating concept that goes back to the 1600s when Johannes Kepler suggested the idea to Galileo Galilei. It wasn't until the beginning of the 21st Century that the Planetary Society created the Cosmos 1 solar sail spacecraft. It launched in June 2005 but a failure meant it never reached orbit. The first successfully launched solar sail was Ikaros, launched by the Japanese Aerospace Exploration Agency it superbly demonstrated the feasibility of the technology.

NASA's Europa Clipper spacecraft, headed to Jupiter's ice-covered moon Europa in October 2024, will carry a laser-etched message that celebrates humanity's connection to water. The message pays homage to past NASA missions that carried similar messages.

As the president of Messaging Extraterrestrial Intelligence, or METI, International, I helped design the message on Clipper with two fellow members of our board of directors: linguists Sheri Wells-Jensen and Laura Buszard-Welcher. METI International is a scientific organization dedicated to transmitting powerful radio messages to extraterrestrial life.

We collected audio recordings in 103 languages, and we decided how to convert these into waveforms that show these sounds visually. Colleagues from NASA etched these waveforms into the metal plate that shields the spacecraft's sensitive electronics from Jupiter's harsh radiation.