On August 2, 1971, at the end of the last EVA of the Apollo 15 mission, Commander David Scott took a few minutes to conduct a classic science experiment in front of the TV camera that had been set up just outside the LM Falcon at the Hadley Rille landing site. Scott, a former Air Force pilot, recreated a famous demonstration often attributed to Galileo (which may or may not have actually been performed by the astronomer in Pisa in 1586) that shows how objects of different masses react the same way to gravity when dropped – that is, they fall at the same rate.
By performing the “acceleration test” in the vacuum environment of space (but where there is still an observable downward pull of gravity) the Earthly factor of air resistance is negated – especially on such a low-mass and low-density object as a falcon feather – thereby creating a more “pristine” setting for the centuries-old experiment than could ever be achieved here.
When you look up at a full or full-ish Moon you can’t help but notice the large dark spots that mark its Earth-facing side. These form the face of what many call the “Man in the Moon” (or the body of a Moon rabbit, to others) and are individually called mare (“MAR-ay”) which is the Latin word for sea. Early astronomers thought they were bodies of water, but in reality they are solidified dark lava flows from ancient lunar impact events that occurred several billion years ago.
One of the biggest lunar seas, Mare Imbrium (see above), had for a while been thought to have been created by the impact of an asteroid or meteorite somewhere around 50 miles across, based solely on computer models.
Now, research conducted by Brown University professor Dr. Peter Schultz—a specialist in lunar and planetary impacts—indicates that the object that formed Mare Imbrium was likely more massive and of much larger size than once thought…perhaps even as big as 190 miles wide.
Everyone knows that Apollo 11 commander Neil A. Armstrong was the first human to set foot on the Moon (and if you didn’t know, that occurred on July 20, 1969 – yes, it really happened). It was a momentous, history-making event that many (like myself) consider one of the most impressive achievements of humankind. But oddly enough, even with high-resolution Hasselblad film cameras there on location, there are very few photos showing Armstrong himself on the surface of the Moon. In fact the one above, an otherwise very nice panorama captured by fellow Apollo 11 astronaut Buzz Aldrin, really is the best image in existence of Armstrong on the Moon.
So…why is that?
This week NASA’s Jet Propulsion Laboratory announced news of an object traveling around the Sun in an orbit that keeps it relatively close to our own planet. The object, a near-Earth asteroid (NEO) less than 300 feet (100 m) across, is designated 2016 HO3 and has in some reports been called a “new” or “mini” moon of Earth…but that’s not entirely true. More accurately 2016 HO3 is what’s known as a quasi-satellite, and is in a temporary (albeit long-lived by human standards) orbit that takes it on a “leapfrog” path around Earth, never getting closer than 38 times the distance to the Moon—about 9.1 million miles.
Discovered in June 2005, distant Pluto’s outermost moon Hydra it thought to have formed during the same collision four billion years ago that created the Pluto-Charon system that we see today. Yet despite its age this 31-mile (50-km) -long moon appears remarkably clean and bright, as witnessed by New Horizons during its close pass through the Pluto system in July 2015.
A crowning achievement of the Cassini mission to Saturn is the discovery of water vapor jets spraying out from Enceladus‘ southern pole. First witnessed by the spacecraft in 2005, these icy geysers propelled the little 320-mile-wide moon into the scientific spotlight. After 22 flybys of Enceladus during its nearly twelve years in orbit around Saturn, Cassini has gathered enough data to determine that there is a global subsurface ocean of salty liquid water beneath Enceladus’ frozen crust—an ocean that gets literally sprayed into space. Now, new findings from Cassini and researchers at the Planetary Science Institute—with a little help from a star called Epsilon Orionis—has shown that at least some of the vapor jets get a boost in activity when Enceladus is farther from Saturn.