How Apollo moon rocks reveal the epic history of the cosmos

Apollo rocks are considered a gateway to a new world of information

Over the course of the six moon landings between 1969 and 1972, astronauts brought back 842 pounds (382 kilograms) of lunar rocks, pebbles, and soil. The lunar lab is a reservoir of hundreds of pounds of moon rocks collected by Apollo astronauts close to a half a century ago. Some of the rocks were vacuum-packed or frozen or stored in gaseous helium preventing them from chemical radiations.

The largest remaining piece of the Apollo 15 moon rock sample 15556 at the Apollo Sample Vault at NASA’s Johnson Space Center.
Credit: Chris Gunn

Inside a locked vault at Johnson Space Center is a treasure few have seen and fewer have touched. Buried within the Apollo samples that came back to Earth, are the clues of lunar origins. Apollo rocks unlock secrets of the universe and help transform our understanding of the cosmos.

“Many of the discoveries that we’ve made in planetary science, not just on the Moon, but on Mercury, on Mars, on some of the asteroids, directly relate to some of the results that we obtained during the Apollo missions.” Lawrence, who works at the Johnson Space Center in Houston, said in an interview with AFP.

Apollo rocks are a gateway to a new world of information, revealing mysteries, opening a window into lunar geology. It has basically revolutionized our understanding of three major concepts: the origin of the moon, nature of the lunar surface and lifelessness of Moon. It took years to correctly interpret these samples using advanced technology but they offered a deeper understanding of the evolutionary history of the universe.

Lunar Samples Are A Time Capsule:

“The Earth is a gigantic recycling machine,” said Juliane Gross, a planetary scientist at Rutgers University. “We have wind, we have rain, we have ice and weather, and so all the rocks weather away.”

The surfaces of the Earth and the moon are very different and dynamic because it is changing continuously. The combination of these factors means that the Earth’s surface is very young and is modified by the presence of life; hence erasing its geologic record.

However, Moon is geologically “dead” with negligible activity. There is no life on the moon and the only factor that changes its surface slowly is the crater’s formation. While life evolved on Earth, “the Moon is lifeless”, preserving the traces of history; making it a time capsule, an archive for the history of our solar system.

Lunar Rocks Are The First Direct Evidence of The Collision That Formed Moon

Before the Apollo mission, scientists were confused regarding the formation of the moon. Some scientists thought that it was an independent object captured by Earth gravity, some considered it a blob of Earth that flung away due to the fast spin of our planet. Others considered that both Earth and moon may have formed from the “protoplanetary disk”.

After the Apollo mission, scientists gained a whole new perspective about the origin of the moon and only “Giant impact hypothesis” seemed to fit in.

Giant Impact Hypothesis-An evolving legacy of Apollo

Around 4.5 billion years ago, according to the prevailing theory of the scientific community, the solar system was a violent place. Around that time, a Mars-sized body known as Theia slammed into an Earth predecessor, forming the earth. The violent reaction results in an ejection of material from both colliding bodies. Debris merges in an earth orbit for next several hundred million years, into what we call today moon. The early moon was covered in an ocean of magma with the heavy minerals forming the core and the lightest ones forming the crust. In this way, the Earth and the moon were formed.

But how does the Apollo rock support this hypothesis? Giant impact hypothesis has been supported by many observations from the Apollo samples which include the following:

Magma Ocean

Moon Rock collected from Apollo 16

The above picture is of a moon rock collected from Apollo’16 made of plagioclase, a rock formed out of molten magma. Plagioclase feldspar mineral (made of sodium and calcium) is a light mineral that floats to the surface of the ocean where it crystallizes forming the crust when molten magma cools down. The presence of the same plagioclase in an Apollo rock is proof of the violent beginning of the moon.

Iron

Apollo rocks revealed that the moon’s core has little iron compared to Earth-just 25% of its total radius. The relative deficiency of iron is an evidence for the giant impact hypothesis that after collision heavy metals like iron sank into the Earth leaving behind lighter elements that were propelled away into what we call moon today.

Volatile Elements

Lunar samples collected from Apollo missions were dry and lacked volatile elements. After the collision, the theory goes, immense heat and energy were generated that may have blown away volatiles from the moon.

According to NASA, “When the young Earth and this rogue body collided, the energy involved was 100 million times larger than the much later event believed to have wiped out the dinosaurs.”

How do Apollo rocks reveal the similarity between the earth and the moon?

Moon rocks collected from the Apollo program have the same chemical fingerprints as earth rocks in terms of oxygen isotopes. Interior structure of the Earth and the moon is also similar i.e. it has a crust, a mantle, and a core.  The similarity between the moon and Earth rocks is also a shred of evidence that supports the giant impact hypothesis. The similarity between both is evidence that they share a common evolutionary history and are formed from the same swirl of the exploded rock.

Moon craters provide a key for unraveling time scales for the geologic evolution

Some of the scientists have used the Apollo rocks to “see beyond the moon”, like a Rosetta stone and unlock the secrets of other planets. Lunar crust “craters” proved to play a vital role in revealing the geologic history of the whole solar system.

Since, Earth’s geologic history has been constantly erased by erosion, tectonics, and volcanism but moon bears the impact of every meteor or asteroid ever crashed into it. Craters are one of the most interesting features in the solar system. And by age-dating lunar craters, we can age-date craters on other planets.

Moon craters can be used as a standard and by comparing the crater of other planets with the lunar crater, we can estimate the age of other planet’s crater. The bigger the craters, the longer they were made.

About 4.5-3.8 billion years ago, asteroids smashed into the larger world, increasing the impact on their surfaces, known as the period of “Late Heavy Bombardment”. Lunar samples provide evidence for this bombardment as they also contain pockmarks due to the hitting of asteroids. By using “crater counting method”, scientists have estimated the age of craters and calculated the time frame for materials smashing into their surface. Analysis of all the data proved the increased impact activity about 3.8-3.9 billion years ago, during the period of Late Heavy Bombardment, which is thought to have lasted between 20  million to 200 million years.

NASA is planning to put boots on the lunar surface by 2024. For now, the astronauts will visit the lunar south pole at a crater called the south pole -Aitken Basin. It is one of the oldest and the deepest moon crater. Lunar exploration plan known as the Artemis program is a two-phased approach: first is to focus on speed, landing astronauts in five years and the second is to establish sustainable human presence over the moon by 2028.

Sustainable human presence over the moon will be the next big thing to uncover new scientific discoveries, demonstrate new technological advancements and will be a good launching ground for the mission to Mars.

Over the course of six Moon landings, planetary scientists have dug a ton of information from the exploration of a small area of Moon. And this information has given scientists a detailed look into the geology of another world.

“The (Apollo) astronauts only directly explored an area that’s roughly the size of a large suburban shopping mall,” Lawrence, who works at the Johnson Space Center in Houston, said in an interview with AFP. “There’s a lot of places on the Moon that we haven’t yet explored.”

Now, Going back and collecting more samples from the areas that are far away and not explored before will help scientists to dig out more mysteries and will give them crucial insight into geologic processes. It is not possible to directly study Earth’s mantle, so Moon is the next big target for the scientists.

“It’s exciting to open up something new”, said Barbara Cohen, a planetary scientist at NASA’s Goddard Space Flight Center who will lead the gas analysis. “We don’t know what we’ll find.”

To fully answer lingering questions, “we need a better global representation of lunar rock types,” Cohen said. And for that, “we need to go back.

Before the Apollo mission, our knowledge was restricted to the limited observations made from the Earth but lunar samples reshaped our understanding of the solar system and gave planetary scientists a whole new perspective. Now scientists are hungry for more and gathering more of them is the foremost reason to go back.

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