Astrophotographer Andrew McCarthy, who last year dropped jaws with a stunningly clear composite photo of the moon made up of 50,000 exposures, is back with a more colorful take on our closest celestial neighbor.
This time, McCarthy composed his first lunar image of 2020 with a blend of around 100,000 exposures taken from his backyard in Sacramento, California. "[This] allowed me to sharpen the image and overcome some of the fuzzing caused by our turbulent atmosphere," he wrote on Instagram.
As McCarthy explains, the colors in these images are real and caused by variations in the composition of the lunar soil or regolith. Formed over billions of years by constant meteorite impacts, lunar soil is estimated by scientists to extend from 3-4 meters (13 feet) to more than 15 meters (50 feet) in the older highlands down to bedrock.
Besides hints of blue and green, the lunar soil also contains orange hues. During the Apollo 17 mission to the moon, astronauts Gene Cernan and Harrison Schmitt were surprised to discover orange soil lurking just beneath the thin veneer of white.
"Oh, hey! Wait a minute... there is orange soil! It's all over! I stirred it up with my feet!," exclaimed Schmitt to Mission Control. Upon further examination, the orange color was found to be volcanic glass, ejected some 3-4 billion years earlier during a lunar eruption.
As McCarthy says, these colors from Earth would be easier to pick out if our eyes were just a bit more sensitive. Nonetheless, their presence is a beautiful reminder that the moon is a lot more complex and colorful that we otherwise might think.
"I find the color really helps tell the story of how some of these features formed billions of years ago," he adds.
To order prints of McCarthy's night sky images or to follow him online, visit his official site.