On April 20, 1972, Apollo 16 astronaut Charles Duke stepped on the moon's surface.

Astronaut Charles M. Duke Jr., Lunar Module pilot of the Apollo 16 mission

He was 36 at the time and is the youngest human in history to ever walk on the moon and he left his family photo over there on april 23,1972

On the back side of the photo a message reads “this is the family of astronaut Duke from planet Earth. Landed on the moon, April 1972”.

On the far left is his oldest son, Charles Duke III, In the front in red is his youngest son, Thomas Duke. Duke and his wife, Dorothy Meade Claiborne, are behind them

"I'd always planned to leave it on the moon, So when I dropped it, it was just to show the kids that I really did leave it on the moon." 

"So just to get the kids excited about what dad was going to do, I said 'Would y'all like to go to the moon with me?'" Duke said. "We can take a picture of the family and so the whole family can go to the moon." Duke told Business Insider.

The photo has since been buzzing on internet and its featured on some popular space books and is a great example of the "human side of space exploration," Duke said.

NASA and Japan’s space agency,JAXA have been wondering if those giant holes on the lunar surface might be entrances to giant caverns resulted from the flowing lava. Recently they have just discovered that these caverns do exist near the Marius Hill region of the Moon which can come out very potential for future lunar colonists to shelter in.

 A view of the eastern Marius Hills, with the Marius crater at top right

As published in Geophysical Research Letters that the discovered large ancient are extremely potential “pristine environment to conduct scientific examination of the Moon’s composition and potentially serve as secure shelters for humans and instruments.” NASA and JAXA scientists took radar and gravity data to make the finding. Being inside these large pits, researchers would be free from UV radiation, and other hazards.

Its depicted that Millions of years ago, occurred lunar volcanic activity, flowing lava carved the surface, and when these channels drained, they oftentimes left a hollow void behind. 

JAXA used a really sophisticated technology to detect such features, they analyzed radar data from the SELENE spacecraft, this instrument can detect lunar lava tubes, which it does by bouncing radar off the lunar surface. 

And by coincident  those cavern area corresponds to locations where NASA, through its GRAIL mission, was able to identify mass deficits

Philadelphia is shown inside a theoretical lunar lava tube. (Image: Purdue University/David Blair)

By combining both findings from SELENE and GRAIL, the team proved the presence of a lava pits, but also the depth and height of the cavity. They extend for one kilometer in height and width. 

Indeed, its time to go back