The Moon may not have ever had liquid water on its surface — despite the use of the term mare, Latin for “sea” and moniker for the large regions of darker material visible from Earth — but liquid did indeed flow on the Moon in ages past… liquid rock, briefly set loose by the impacts that formed its ubiquitous craters.
When large meteorites impacted the Moon, crust at the site would melt and get flung outwards, flowing downhill as rivers of rock and creating streams and pools of melted material before cooling and solidifying. There the rivers would remain, a permanently-hardened testament to the event that made them.
The image above, part of a NAC scan acquired by NASA’s Lunar Reconnaissance Orbiter on March 9, shows a solidified melt flow dating back to the creation of Tycho crater approximately 108 million years ago –which may sound like a long time but it’s actually very recent for large-scale lunar features.
The flow is interrupted by a younger, 400-meter-wide crater that impacted the lunar surface along its length. Since it punches through the melt flow as well as the local surface, it would be a great place for future astronaut geologists to explore!
Taken under slightly different lighting conditions, the image below shows a large melt pond that the flow above terminates in. The pond is about 4500 meters long by 2100 meters across (2.8 x 1.3 miles).
Such images wouldn’t be possible without the awesome Lunar Reconnaissance Orbiter. Launched on June 18, 2009, LRO explores the lunar surface from an altitude of only 50 km (31 miles). Read more on the LRO site here.
A team of researchers at India’s Physical Research Laboratory (PRL) claims it has found evidence of relatively recent volcanic activity on the Moon, using data from NASA’s Lunar Reconnaissance Orbiter and the Chadrayaan-1 spacecraft. According to the findings the central peak of Tycho crater contains features that are volcanic in origin, indicating that the Moon was geologically active during the crater’s formation 110 million years ago.
In an article by the Deccan Herald, a Bangalore-based publication, the PRL researchers claim that vents, lava channels and solidified flows of inner crustal material found within Tycho were made as recently as 100 million years ago — after the creation of the crater.
This could indicate that there was pre-existing volcanic activity within the Moon at the site of the Tycho impact, lending credence to the idea that the Moon was recently geologically active.
In addition, large boulders ranging in size from 33 meters to hundreds of yards across have been spotted on Tycho’s central peaks by LRO, including one 400-foot (120-meter) -wide specimen nestled atop the highest summit. How did such large boulders get there and what are they made of?
The researchers hint that they may also be volcanic in origin.
“A surprise findings revealed the presence of large boulders–about 100 meter in size –on top of the peak. Nobody knew how did they reach the top,” said Prakash Chauhan, a PRL scientist.
Without further studies it’s difficult to determine the exact origin and ages of these lunar formations. The team awaits future research by Chandrayaan-II, which will examine the Moon from orbit as well as land a rover onto the lunar surface. Chandrayaan-II is expected to launch in early 2014.
The PRL team’s findings were published in the April 10 issue of Current Science.