The Air on Mars
Specimen Notes from the Mini Museum: Martian Atmosphere
This post comes in part from a project update for the Second Edition of the Mini Museum.
The Mini Museum is the realization of my life long dream. 5,030 people in 68 countries backed the First Edition of the Mini Museum and that adventure has lead to an entirely new journey.
Over the coming weeks, I’m going to share stories about the creation of the Second Edition, including the challenges we face with each and every specimen.
Today, the atmosphere of Mars is roughly 100 times thinner than that of Earth and composed primarily of carbon dioxide. Like Earth and Venus, the Martian atmosphere also contains a small percentage of the noble gas Argon. However, unlike Earth and Venus, the ratio of Argon isotopes in the Martian atmosphere is unique and the mixture skews towards the heavier isotopes. This suggests that the lighter isotopes (along with many other elements) escaped from the Martian atmosphere sometime in the deep past.
Just how Mars came to lose its atmosphere is a subject of intense study. Some theories suggest that the loss of the planet’s magnetic field is to blame while others look to the timing of the Late Heavy Bombardment (LHB) during which large numbers of asteroids and comets struck the inner planets of the solar system 4.1–3.8 billion years ago.
As we’re learning now in great detail, it is highly likely that prior to the loss of the atmosphere Mars was a warmer and wetter planet. Direct evidence for a warm and wet Mars exists in the dusty echoes of rivers and lakes on the surface planet, but within the soil scientists have also discovered evidence of carbonates which suggests a thicker atmosphere with significant moisture. The image to the left comes from the Keck Observatory and shows what Mars how much water Mars might have held at one time.
Whether this environment could harbor life is unknown, but what we do know is that roughly four billion years ago the Mars lost most of its atmosphere and has since remained mostly cold and dry with periods of intense volcanic activity.
“The central edifice of Olympus Mons has a summit caldera 24 km above the surrounding plains. Surrounding the volcano is an outward-facing scarp 550 km in diameter and several kilometers high. Beyond the scarp is a moat filled with lava, most likely derived from Olympus Mons. Farther out is an aureole of characteristically grooved terrain, just visible at the top of the frame.”
One such period of volcanic activity created the rock which would eventually become the Zagami meteorite. Scientific studies place the age of the basaltic rock which makes up Zagami at roughly 170,000,000 years old, and analysis of exposure to cosmic rays suggests that the rock was ejected from the planet some 2.5 million years ago.
When a large body, such as an asteroid or comet, strikes a planet it can create enough force to eject pieces of the planet into space. The force of such an impact creates tremendous heat which melts the rock, creating glass pockets or “shock melt” veins which can trap molecules from the surrounding atmosphere. This is exactly what happened with Zagami, which floated through space for millions of years until landing in rural Nigeria in 1962.
Below, Robert Haag, the famous meteorite hunter from whom we purchased Zagami, tells the tale of the meteorite’s fall and discovery in 1962 in rural Nigeria:
“The farmer was trying to chase the cows out of his corn field when he heard a tremendous explosion and was buffeted by a pressure wave. Seconds later, there was a puff of smoke and a thud, as something buried itself in the soft dirt only ten feet away. Terrified that it was an artillery shell or bomb, the man waited for a few minutes before going to investigate. What he saw was a black rock at the bottom of a two-foot hole.”
After trading most of his own personal meteorite collection for what would become the only publicly available Zagami, Robert Haag donated slices to NASA [LINK] and several universities for additional analysis. The research resulting from these donations detailed above makes Zagami one of the most studied meteorites in history, and led to the discoveries about the Martian atmosphere that were confirmed by NASA’s Curiosity Rover in 2013.
If you look at the geochemical makeup of Zagami, you will see that it is unlike the asteroids described in the last update. Being basaltic rock, or effectively Martian lava, Zagami is composed almost entirely of silicon. This makes it rather fragile, so preparing Zagami is delicate work.
To begin preparation, we stabilize the meteorite using a solution of amorphous silica. This penetrates the rock and creates new crystaline structures at a microscopic level while preserving the original material. This is important not only for the preparation of the specimen itself but also to keep it intact when it is encased in acrylic.
Given such a limited amount of rare material, Zagami must be prepared under a microscope with careful and measured cuts. This requires weeks of calm work, as only a small number of specimens can be produced each day.
Each batch of specimens is weighed and evaluated against previous batches. Later, each specimen is reviewed once more and placed on a sheet of silicone and sealed for transport.
Preparing Zagami was a fascinating experience. Every specimen in the Mini Museum has its challenges, but some have to go a little farther than others.
Spending hundreds of hours under the microscope, it is hard not to think about the long adventure this specimen has undergone. It was once lava on the surface of Mars, then after millions of years on the surface it survived a massive collision and journeyed through space to Earth. Then, it became one of the most studied meteorites in human history. Still, even with all of this amazing backstory, I am struck by the simplicity of the discovery of this incredible meteorite.
“Science is no more than an investigation of a miracle we can never explain, and art is an interpretation of that miracle.” ~ Ray Bradbury, The Martian Chronicles
I hope you’ve enjoyed this post. I am looking forward to sharing more of this information with all of you as the project goes forward.
Now, it’s back to work!
Hans Fex, Creator and Chief Curator for the Mini Museum
