When NASA’s Perseverance rover used its laser to tease aside some pale rocks mendacity round in Jezero Crater in 2025, scientists didn’t count on something out of the peculiar.
Little did they know what was in retailer.
The rocks contained one thing by no means earlier than discovered on Mars – a mineral that, right here on Earth, can represent literal treasure.
The mineral was corundum, the crystalline materials that varieties rubies and sapphires. And there was even a whiff of chromium, which provides rubies their distinctive reddish-pinkish hues.
“Very unexpectedly,” wrote a group led by geochemist Ann Ollila of Los Alamos Nationwide Laboratory in a conference abstract, “SuperCam’s TRL evaluation of three plagioclase-rich float rocks within the crater rim have been discovered to exhibit clear signatures of chromium-bearing corundum.”
Now, the researchers have printed their full evaluation in Geophysical Research Letters – and carried out laboratory comparisons that exposed hanging similarities between the Martian sign and people of valuable gems on Earth.
It is the primary time corundum has been recognized in a Martian setting, and the invention is outstanding not as a result of the minerals are ones we contemplate useful, however as a result of the circumstances wherein they sometimes kind aren’t simply defined on Mars.
“Its formation usually requires bulk compositions enriched in aluminum and depleted in silicon and sometimes varieties at both excessive temperatures or in affiliation with tectonic processes,” Ollila and her colleagues write of their paper.
“Therefore, its detection in Martian rocks is shocking.”
Mars does not lack within the warmth division, or not less than, it did not previously. Its floor is riddled with volcanic options, and Jezero Crater incorporates a wealth of igneous materials.
No, the issue right here lies within the chemistry.
Corundum is the crystalline type of aluminum oxide, and its formation normally requires plenty of aluminum and never a lot silicon – as a result of if there are silicate minerals round, they will bogart all of the aluminum to kind aluminum-silicate rocks similar to plagioclase feldspar.
You have most likely already noticed the corundum conundrum. All three corundum detections made by Perseverance have been in chunks of rock dominated by plagioclase. That is one dilly of a pickle – not least as a result of the rocks have been discovered in several places alongside the crater rim.
It isn’t that plagioclase and corundum cannot coexist. It is that the circumstances for his or her coexistence are tough to return by on Mars.
The three rocks – named Hampden River, Coffee Cove, and Smiths Harbour – have been pale plagioclase-rich chunks, and all three have been what are generally known as float rocks. These are chunks of rock sitting on the bottom which can be now not hooked up to the bedrock they fashioned in, that means they could have been transported from elsewhere.
Float rocks are attention-grabbing targets for examine as a result of they will inform us in regards to the broader geology of Mars with out the rover having to journey to a distinct space.
One after the other – in March, April, and July of 2025 – Perseverance examined every rock utilizing time-resolved luminescence (TRL) spectroscopy. It makes use of a laser to excite atoms inside minerals, then measures the attribute mild they emit as they subside to their regular state.
When Perseverance carried out this evaluation on all three of the plagioclase samples, the ensuing spectra returned the distinctive signature of chromium-bearing corundum.
So, disappointingly, no glowing rubies scattered throughout the floor of Mars like a careless dragon had spilled a hoard – however the spectral proof for tiny grains of chromium-bearing corundum trapped inside three separate plagioclase chunks.
Nonetheless, when the researchers in contrast these spectra to commensurate spectra from ruby, sapphire, and diaspore on Earth, issues received attention-grabbing.
All three Martian rocks had two outstanding luminescence peaks at wavelengths of 692.7 and 694.1 nanometers – the attribute type of peaks produced in corundum when chromium atoms substitute some aluminum atoms, as they do in ruby.
And in Smiths Harbour – the one pattern for which this was measured – the glow lingered for about 3 milliseconds, squarely within the vary measured for terrestrial corundum.
So are there rubies on Mars? Nicely, perhaps. However the extra attention-grabbing query is: How does Mars make one thing that behaves like rubies?
And the reply could be staring us within the face: Jezero Crater itself.
There are a number of methods the corundum may have fashioned, together with by way of magma or interactions between rock and sizzling fluids. However Ollila and her colleagues favor one other chance – the colossal influence that gouged Jezero Crater out of the Martian floor billions of years in the past.
Giant impacts topic rocks to super warmth and stress, producing circumstances related to people who create metamorphic minerals deep inside Earth’s crust. Corundum has even been present in impact-altered rocks on Earth and the Moon.
The clues are circumstantial, however compelling.
The corundum on Mars happens in tiny grains; the rocks have been discovered on the rim of Jezero Crater; and so they have been sitting near rocks interpreted as influence breccias – chunks of rock fashioned in an influence.
The researchers even suppose fluids interacting with the rocks could have helped create the aluminum-rich, silicon-poor chemistry that will have facilitated corundum’s formation; there may be proof for previous hydrothermal exercise in Jezero, too.
Associated: Scientists Cracked Open a Mars Meteorite And Found a Big Surprise
Different explanations can’t be dominated out, and there is solely a lot we are able to do right here from Earth when the minerals are half a Photo voltaic System away.
Discovering the outcrop from which the float rocks originated would assist. Higher nonetheless can be getting a chunk of it again to Earth.
That is a powerful case for reviving the Mars pattern return mission that has fallen by the wayside.
“If a core pattern have been obtained from this outcrop and returned to Earth,” they write, “vastly extra analyses may very well be performed to conclusively decide how this corundum fashioned, which would supply a extra full understanding of Martian historical past.”
The findings have been detailed in Geophysical Research Letters.
This text was fact-checked by Rachel Garner and edited by Rebecca Dyer. Whereas we delight ourselves on our course of, we’re solely human. Should you spot a mistake, please let us know.
