There may be water on all rocky planets

If you asked someone who was reasonably scientifically educated on how the Earth got its water, they would probably tell you it came from asteroids – or maybe even comets and planetesimals – that crashed on our planet in its early days. There are details, nuances, and uncertainties surrounding that idea, but it’s widely believed that it’s the most likely reason the Earth has so much water.

But a new explanation for Earth’s water is emerging. It says water comes for the journey when the Earth was formed from the solar nebula.

If that’s correct, it means that most rocky planets could have water for at least part of their life.

A new paper presents evidence suggesting that water is not being delivered to rocky planets but is formed as part of the planet’s formation process. The title of the article is “Early oxidation of the Martian crust triggered by impacts”. The lead author is Zhengbin Deng, assistant professor at the Center for Star and Planet Formation, Globe Institute, University of Copenhagen. The study is published in the journal Science Advances.

“There are two hypotheses about the emergence of water. One is that it arrives on planets by accident, when asteroids containing water collide with the planet in question, “said co-author Professor Martin Bizzarro in a press release. Bizarro is also from the Center for Star and Planet Formation at the ‘University of Copenhagen.

“The other hypothesis is that water emerges in connection with the formation of the planet. Our study suggests that this hypothesis is correct and, if it is true, it is extremely exciting, because it means that the presence of water is a bioproduct of the planet’s formation process, ”explains Martin Bizzarro.

Evidence for this hypothesis comes from a small meteorite called Black Beauty. Black Beauty (aka Northwest Africa 7034) is a piece of Mars that fell to Earth and was discovered in the Sahara Desert in 2011. It was mysterious because it defied classification. Eventually, the scientists determined that it represented a new classification of Martian meteorites which they called “Martian (basaltic breach)”.

Black Beauty is really old; its components are 4.45 billion years old according to this study. It is the second oldest Martian meteorite ever found. It is so ancient that it comes from the original crust of Mars. But Black Beauty also has the highest water content of any Martian meteorite.

According to this research, Mars had water for the first 90 million years of its existence. This is long before there was enough time for asteroids to bomb the planet and supply water. The water must have another source.

Black Beauty forced scientists to ask a question: whether the water of Mars – and by extension the water of the Earth – was released from collisions with water bodies such as asteroids, how did the planets have water in their early days? 90 million years? There was simply not enough time for the asteroids to carry water.

“It suggests that water emerged with the formation of Mars. And it tells us that water can occur naturally on planets and doesn’t require an external source like water-rich asteroids, ”he says.

The researchers obtained about 50 grams of Black Beauty for this study and developed a new method for unlocking the secrets of the meteorite. They took 15 grams of it and crushed it, melted it, then analyzed it.

The analysis revealed something shocking. Although the impactors did not provide that water, they did provide evidence for the source of that water.

“We have developed a new technique that tells us that Mars in its infancy suffered one or more severe impacts with asteroids. The impact, Black Beauty reveals, created kinetic energy that released a lot of oxygen. And the only mechanism that could probably have caused the release of such large amounts of oxygen is the presence of water, ”said Zhengbin Deng.

Much of the evidence in this study relates to oxygen. Oxygen is a swinger; he likes to combine with almost anything. As it combines with other elements on Mars, the resulting minerals bear traces of their origins as isotopes. By tracing the origins of compounds containing elements such as iron and titanium, the researchers developed a kind of timeline of the evolution of Martian rocks as they melted and solidified.

This research focused on 15 Black Beauty igneous clasts. The team performed a detailed analysis of these clasts, using different types of spectroscopy.

“These clasts have been proposed to be the product of a first recast, probably by impact, of the primary crust derived from the Martian mantle. Hence, these igneous clusters can provide information about the ancient surface of Mars, allowing us to investigate the physicochemical conditions that existed on the planet’s surface, including the fugacity of oxygen at the time of the crust’s reprocessing. This information is fundamental to limit the time of constitution of the hydrosphere and the atmosphere of Mars and, therefore, the potential for initial habitability “, explain the authors.

Titanium isotopes played a key role in the work. “Therefore, the combination of chemical and isotopic compositions of Ti can be used to determine the thermal and / or redox magma histories of igneous rocks, in other words, T.–fOR₂ paths during the evolution of magma “, the authors write in their article.

Okay as far as it goes. But how did a cold planet like Mars keep that water at a time when the Sun was much younger and weaker? How did that water settle in ancient lakes and rivers – and even oceans – that we find evidence of today?

According to the researchers, the same impact that released all that oxygen also released greenhouse gases. Those gases heated the atmosphere enough to make liquid water persist. According to Zhengbin Deng, “this means that the CO2-rich atmosphere may have caused a rise in temperature and thus allowed the presence of liquid water on the surface of Mars.”

But there is a cautionary note about these findings and it comes from the authors themselves. “The high-?¹⁷The water component on primordial Mars can represent either water delivered by impacting material such as water-rich asteroid bodies or, alternatively, water balancing with photochemicals from the primitive Martian atmosphere. Our data cannot discriminate between these two possibilities. “

But that doesn’t mean their data is completely weak. “However, the origin of the impact for the NWA 7533/7034 basaltic clasts is established by their enrichment in elements highly siderophilic. “They also point out that their interpretation of the data is in line with other evidence” … indicating that the first 8-11 km of the Martian crust are severely fractured. It has been proposed that such early bombardment episodes may have induced surface temperatures elevated on Mars, resulting in an initial warm and humid climate that is implied by ancient records of river activity. “

It is rarely a theory confirmed or disproved in the wake of a single study. This is no exception. But it brings out another recent study that examines the origins of Earth’s water.

This recent research suggests that Earth’s water actually came from the solar nebula shortly after the planet was formed. Not the water itself, but the hydrogen and oxygen that got stuck inside the planet’s mantle. Over time, those elements have combined in the water. If this study is correct, the hydrogen and oxygen present in the mantle of Mars could also have combined to form water from violent impacts long before asteroids and other bodies could have delivered it.

Or it could be that Earth’s water and Mars’s water had multiple sources. It could come from both an asteroid impact and the solar nebula.

There appears to be a possibility that rocky planets may have water soon more often than not and that delivery by asteroids is not required. Either way, the conversation about the source of water on the rocky planets just got more interesting.

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