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Early on the morning of Jan. 31, 1961, a chimpanzee named Ham, outfitted in a diaper, waterproof pants and a space suit, was sealed into a capsule and loaded onto a Mercury-Redstone 2 spacecraft in Cape Canaveral, Fla. Six hours later, Ham the Chimp, named after Holloman Aeromedical Research Laboratory at Holloman Air Force Base in Alamogordo, N.M., where he was trained, became the first hominid to travel into space.

Not so long ago, Mercury was the least-studied planet in the inner solar system, known only from Earth-based observations and from Mariner 10’s brief flyby in the 1970s. In 2011, the MESSENGER spacecraft began orbiting Mercury, imaging the planet’s crater- and fault-scarred surface before crashing into it, as planned, in 2015. As MESSENGER spiraled downward, it took a last series of high-resolution images, analyses of which are revealing new information about the planet’s surface geology, including evidence for recent tectonic activity.

In May, a new planetary system was discovered just 40 light-years from Earth, including three Earth-sized planets orbiting around their red dwarf sun in a temperature range that could potentially harbor life. Now, a follow-up study on the system has found that the two innermost planets are primarily rocky with compact atmospheres, as opposed to inhospitable gas giants, like Jupiter.

Periodically, micrometeoroids strike one of the four Galilean moons of Jupiter — Io, Europa, Ganymede and Callisto — sending dust into space, some of which enters into orbit around the gas giant. Recently, researchers charting the dusts’ orbits spotted some peculiar patterns, including some particles orbiting Jupiter in a retrograde fashion, by circling, when viewed from above, clockwise rather than counterclockwise.