Apollo 11 astronaut Edwin "Buzz" Aldrin salutes the American flag on the surface of the moon on July 20, 1969. Aldrin was the second man to step foot on the lunar surface. The first was Neil Armstrong, Apollo 11's mission commander.
Apollo 11 astronaut Edwin "Buzz" Aldrin salutes the American flag on the surface of the moon on July 20, 1969. Aldrin was the second man to step foot on the lunar surface. The first was Neil Armstrong, Apollo 11's mission commander.
NASA/Hulton Archive/Getty Images
Apollo 11's crew is pictured before the launch. From left are Armstrong, Michael Collins and Aldrin. Collins piloted the command module that orbited the moon, while Armstrong and Aldrin spent time on the surface.
Apollo 11's crew is pictured before the launch. From left are Armstrong, Michael Collins and Aldrin. Collins piloted the command module that orbited the moon, while Armstrong and Aldrin spent time on the surface.
NASA/Hulton Archive/Getty Images
A Saturn V rocket launched Apollo 11 into space on July 16, 1969.
A Saturn V rocket launched Apollo 11 into space on July 16, 1969.
Ralph Morse/The LIFE Picture Collection/Getty Images
Former US President Lyndon B. Johnson and then-Vice President Spiro Agnew were among those watching the launch at Florida's Kennedy Space Center.
Former US President Lyndon B. Johnson and then-Vice President Spiro Agnew were among those watching the launch at Florida's Kennedy Space Center.
NASA
It took the crew 76 hours to travel 240,000 miles from the Earth to the moon.
It took the crew 76 hours to travel 240,000 miles from the Earth to the moon.
NASA
The Apollo 11 spacecraft consisted of a command module, Columbia, and a lunar module, Eagle. This image, taken from the Eagle lunar module, shows the Columbia command module pulling away near the lunar surface.
The Apollo 11 spacecraft consisted of a command module, Columbia, and a lunar module, Eagle. This image, taken from the Eagle lunar module, shows the Columbia command module pulling away near the lunar surface.
NASA/Corbis Historical/Getty Images
Armstrong works outside the Eagle module shortly after becoming the first man to step foot on the lunar surface. There are few photographs of Armstrong on the moon since he was the one taking most of the photos.
Armstrong works outside the Eagle module shortly after becoming the first man to step foot on the lunar surface. There are few photographs of Armstrong on the moon since he was the one taking most of the photos.
NASA/Hulton Archive/Getty Images
Fans at a Philadelphia Phillies baseball game cheer after the announcement that the Eagle had made a safe lunar landing on July 20, 1969.
Fans at a Philadelphia Phillies baseball game cheer after the announcement that the Eagle had made a safe lunar landing on July 20, 1969.
Bill Ingraham/AP
Armstrong is pictured aboard the Eagle just after the historic moonwalk. As Armstrong lowered himself to the surface, people watching around the world heard him call it "one small step for man, one giant leap for mankind." Armstrong later said he had intended to say "a man" and thought he had. <a href="https://www.cnn.com/2013/06/04/tech/armstrong-quote/index.html" target="_blank">Studies have been carried out over the years</a> to discover whether he uttered that one little sound. Either way, his intention was clear.
Armstrong is pictured aboard the Eagle just after the historic moonwalk. As Armstrong lowered himself to the surface, people watching around the world heard him call it "one small step for man, one giant leap for mankind." Armstrong later said he had intended to say "a man" and thought he had. Studies have been carried out over the years to discover whether he uttered that one little sound. Either way, his intention was clear.
NASA/Corbis Historical/Getty Images
A view of Earth appears over the lunar horizon as Apollo 11's command module comes into view of the moon.
A view of Earth appears over the lunar horizon as Apollo 11's command module comes into view of the moon.
NASA/Hulton Archive/Getty Images
Aldrin walks on the surface of the moon. He and Armstrong spent a little over two hours collecting rock samples and data near the moon's Sea of Tranquility region. They also left behind a plaque signed by all three crew members and President Richard Nixon. The plaque reads: "Here men from the planet Earth first set foot upon the moon, July 1969 A.D. We came in peace for all mankind."
Aldrin walks on the surface of the moon. He and Armstrong spent a little over two hours collecting rock samples and data near the moon's Sea of Tranquility region. They also left behind a plaque signed by all three crew members and President Richard Nixon. The plaque reads: "Here men from the planet Earth first set foot upon the moon, July 1969 A.D. We came in peace for all mankind."
NASA
Aldrin's family and friends watch the mission on television from his home in Texas. Aldrin's then-wife, Joan, is in the polka-dot shirt. ABC, CBS and NBC spent $11 million to $12 million to cover the mission from July 20-21.
Aldrin's family and friends watch the mission on television from his home in Texas. Aldrin's then-wife, Joan, is in the polka-dot shirt. ABC, CBS and NBC spent $11 million to $12 million to cover the mission from July 20-21.
Lee Balterman/The LIFE Picture Collection/Getty Images
An astronaut's boot print leaves a mark on the lunar surface.
An astronaut's boot print leaves a mark on the lunar surface.
NASA/Hulton Archive/Getty Images
Aldrin, the lunar module pilot on the Apollo 11 mission, is pictured before the moon landing.
Aldrin, the lunar module pilot on the Apollo 11 mission, is pictured before the moon landing.
NASA
Apollo 11 photographed this view of Earth as it approached on its return from the moon.
Apollo 11 photographed this view of Earth as it approached on its return from the moon.
AFP/Getty Images
US Navy personnel assist the astronauts after their reentry vehicle landed safely in the Pacific Ocean on July 24, 1969.
US Navy personnel assist the astronauts after their reentry vehicle landed safely in the Pacific Ocean on July 24, 1969.
AP
NASA officials and flight controllers celebrate the successful conclusion of the mission.
NASA officials and flight controllers celebrate the successful conclusion of the mission.
NASA
Nixon spends time with the astronauts, who were in a quarantine trailer for their first few days back on Earth. From left are Armstrong, Collins and Aldrin. Since Apollo 11, only 10 other people have walked on the moon. The last was in 1972 during the Apollo 17 mission.
Nixon spends time with the astronauts, who were in a quarantine trailer for their first few days back on Earth. From left are Armstrong, Collins and Aldrin. Since Apollo 11, only 10 other people have walked on the moon. The last was in 1972 during the Apollo 17 mission.
MPI/Getty Images
The Apollo 11 moon landing, in photos

Editor’s note: A version of this story appeared in CNN’s Wonder Theory science newsletter. To get it in your inbox, sign up for free here.

CNN  — 

As the full moon shines in the night sky this weekend, take a moment to revel in its beauty and search for a large, dark plain.

The surface feature is Mare Tranquillitatis, or the Sea of Tranquility, where the Apollo 11 mission landed on the afternoon of July 20, 1969.

The full moon won’t peak until 6:17 a.m. ET Sunday, but the silvery orb will still appear at its best Saturday, the 55th anniversary of NASA astronauts Neil Armstrong and Buzz Aldrin conducting humankind’s first moonwalk.

Now, as NASA and other space agencies plan for a more established human presence on the moon through the Artemis program, it turns out that the Sea of Tranquility may have an unexplored treasure worth revisiting.

Lunar update

Scientists have discovered a large lunar cave connected to a pit found within the moon's Sea of Tranquility.
Scientists have discovered a large lunar cave connected to a pit found within the moon's Sea of Tranquility.
NASA/Goddard/Arizona State University

Scientists have found a subterranean cavity beneath the Sea of Tranquility, and it may provide shelter for future lunar astronauts in the form of a cave.

Lunar caves, or underground passages formed by volcanic processes during the moon’s early history, are connected to pits covering the lunar surface.

The long, wide cave, found by reviewing archival NASA data, could be used to protect astronauts from harsh radiation and extreme temperature swings as well as provide a new avenue to study lunar rocks.

Other worlds

Astronomers have detected an exoplanet with an orbit shaped like a cucumber that may be turning into another type of world.

The unusual orbit, which changes temperatures on TIC 241249530 b from a warm summer day to hot enough to melt titanium, may be a sign that the planet is moving closer to its star.

Astronomers estimate that in hundreds of millions of years, the planet will only take a few days, rather than six months, to orbit its star and become a hot version of Jupiter.

Separately, the European Space Agency plans to send a spacecraft named Ramses to accompany the asteroid Apophis as it makes a safe, close approach of Earth — 10 times nearer than the moon — in April 2029. The spacecraft could capture quakes and landslides on the space rock as it is affected by Earth’s gravity.

Fantastic creatures

Before his nip and tuck (left), Hamilton hated to open his eyes. After his eyelids were fixed (right), he is wide-eyed.
Before his nip and tuck (left), Hamilton hated to open his eyes. After his eyelids were fixed (right), he is wide-eyed.
Lori Hilton

If pets with flat faces, such as French bulldogs and Persians, or puffy cheeks like Maine coons, squint and show behavioral problems, they may have a painful condition: eyelid disease.

Some dog and cat breeds are genetically more likely to have issues with malformed eyelids, which causes the eyelashes to scrape against the corneas.

But what humans would call cosmetic surgery is helping pets like Hamilton, a 4-year-old English bulldog, overcome the pain of misshapen eyelids.

“These nip and tucks are not cosmetic; they are critical to the health of the animal,” said Dr. Dana Varble, chief veterinary officer for the North American Veterinary Community.

The wonder

The Curiosity rover was about to settle in to a new exploration site on Mars when it crunched over a rock — and happened to make the “most unexpected” discovery during its 12-year mission to date, according to mission scientists.

Curiosity’s wheels revealed that the inside of the rock was something never seen before on the red planet: yellowish-green sulfur crystals. And it turns out there are a whole field of them within an ancient channel carved into the side of Mars’ Mount Sharp.

But scientists don’t know how, when or why the sulfur formed on Mars, creating a new riddle for the rover’s team to solve.

Meanwhile, the newly inaugurated African Space Agency is launching satellites to improve quality of life on Earth, such as monitoring water quality and preventing illegal mining and fishing.

A long time ago

A fossil revealing the complete side view of the ancient shark Ptychodus, with almost all skeletal elements, was found in Mexico.
A fossil revealing the complete side view of the ancient shark Ptychodus, with almost all skeletal elements, was found in Mexico.
Courtesy Dr. Jürgen Kriwet

While dinosaurs roamed Earth during the Cretaceous Period, sharks with unusual teeth swam the seas.

Sharks in the genus Ptychodus had rows of large, rounded chompers that crushed shelled prey. But scientists have only been able to speculate on the predators’ appearance after finding just teeth.

Paleontologists recently unearthed a nearly complete skeleton of the ancient shark in the Mexican state of Nuevo Léon, unraveling the mystery of the prehistoric fish’s appearance.

Separately, cut marks on the fossilized remains of a giant armadillo-like creature in Argentina reveal that humans butchered the animal more than 20,000 years ago — and that the earliest people in the Americas settled there earlier than expected.

Explorations

Delve into these unexpected stories:

— Experts in New Zealand are determining whether a creature that washed ashore is a spade-toothed whale — a species considered nearly mythical because scientists have never recorded a live sighting.

— NASA transmitted Missy Elliott’s “The Rain (Supa Dupa Fly)” about 158 million miles to Venus, marking the first time a hip-hop song has been sent to space.

— In Cambodia, a record-breaking number of Siamese crocodile eggs just hatched in the wild, providing hope for a critically endangered species that had nearly been driven to extinction.

— A blazing meteor soared over New York City this week and disintegrated above New Jersey, and sky-gazers captured videos of the rare event.

Like what you’ve read? Oh, but there’s more. Sign up here to receive in your inbox the next edition of Wonder Theory, brought to you by CNN Space and Science writers Ashley Strickland and Katie Hunt. They find wonder in planets beyond our solar system and discoveries from the ancient world.