It’s craters all the way down! – NASA Ranger missions

Some Moon missions that ended up in a crash were a success! We’re talking about the NASA Ranger missions that intentionally hit the Moon.

Photographs sent by NASA’s Ranger 7 spacecraft, 90 seconds before smashing into the Moon. The top two images are about 15 km across and the bottom ones 5.5 km across. Credit: NASA

The robotic Ranger missions were critical for NASA to land humans on the Moon in 1969. To ensure a safe landing, it was important to know what kind of terrain the Moon hosts at local scales. And what are the hazards to look out for.

Before the advent of the space age, the only way to capture images of the Moon was via large Earth-based telescopes, which couldn’t discern much. Post-that, even capturing from lunar orbit wouldn’t gives results as sophisticated as today’s. To truly determine how the local lunar surface was like, NASA decided to send “Ranger” spacecraft smashing into the lunar surface! As each craft in the Ranger Program descended, it would send back images to Earth in near real time via its TV camera setup.

Ranger spacecraft diagram. Credit: NASA

The captured images would boast a 100 to 1,000 times higher resolution for local features than any other method at the time. It is only now that even from orbit, NASA’s Lunar Reconnaissance Orbiter can image areas at a best resolution of 0.5 m/pixel. ISRO’s newly put lunar orbiter, Chandrayaan 2, can do a best of 0.3 m/pixel.

When the first such successful mission of the Ranger Program, Ranger 7, took the fall in 1964, everyone was surprised. Even vast plains on the Moon which seemed benign turned out to have craters all over them when looked up close. The Moon turned out to be a land of craters more than anything else, at large scales or small. Here’s a video made from Ranger 7’s camera shots, captured from over 2000 km to just 500 m above the Moon’s surface, as it descends into an eventual crash.

NASA Ranger 7 descending on the Moon. It’s craters all the way down! Image credits: NASA

The Ranger 8 and 9 missions all but confirmed the inevitable fact that the Moon is riddled with craters. In all, the Ranger missions sent over 15,000 high-resolution photographs to Earth. It is from this data that NASA selected safe landing regions for the Apollo missions, in what resulted in the eventual “One small step for man, one giant leap for mankind”.

The Ranger missions were, literally and figuratively, a smashing success!

It’s craters all the way down on the Moon, one could say. As we learnt in last week’s guest Moon Monday by NASA Program Scientist Sarah Noble, the Moon is cratered even at microscopic scales!



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