If you asked someone with reasonable scientific knowledge how the Earth got its water, they would probably tell you that it came from asteroids – or maybe also comets and planetesimals – that crashed into our planet in its infancy. There are details, nuances, and uncertainties surrounding this idea, but it’s generally believed to be the most likely reason Earth has so much water.
But a new explanation for Earth’s water is emerging. He says water comes for the ride when Earth formed from the solar nebula.
If this is correct, it means that most rocky planets could have water for at least part of their life.
A new article presents evidence suggesting that water is not delivered to rocky planets but forms as part of the process of forming the planet itself. The title of the article is “Early Oxidation of the Martian Crust Triggered by Impacts”. The main 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.
âThere are two hypotheses on the emergence of water. One is that it arrives on planets by accident, when asteroids containing water collide with the planet in question, âsaid 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.
âThe 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 process of planet formation, âexplains Martin Bizzarro.
The proof for this hypothesis comes from a small meteorite named 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 categorization. Finally, the scientists determined that this was a new classification of Martian meteorites which they named “Martian (basaltic breccia)”.
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 discovered. It is so old 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 asteroids have time to bombard the planet and deliver water. The water must have some other source.
Black Beauty forced scientists to ask a question: If the water on Mars – and by extension the water on Earth – was supplied by collisions with aquifers like asteroids, how did the planets get hurt? water during their first 90 million years? There just wasn’t enough time for the asteroids to deliver the water.
âThis suggests that water emerged with the formation of Mars. And it tells us that water can be naturally present on planets and does not require an external source like water-rich asteroids,â he says.
The researchers obtained approximately 50 grams of Black Beauty for this study, and they developed a new method to unlock the secrets of the meteorite. They took 15 grams of it and crushed it, dissolved it, then analyzed it.
The analysis revealed something shocking. Although the impactors did not provide this water, they did provide evidence of the source of this water.
âWe have developed a new technique that tells us that early Mars suffered one or more severe asteroid impacts. The impact, reveals Black Beauty, created kinetic energy that released a lot of oxygen. And the only mechanism that could possibly have caused the release of such large amounts of oxygen is the presence of water, âZhengbin Deng said.
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 like iron and titanium, researchers have developed a sort of timeline of the evolution of Martian rocks as they melt and solidify.
This research focused on 15 igneous clasts of Black Beauty. The team performed a detailed analysis of these clasts, using several types of spectroscopy.
âIt has been proposed that these clasts are the products of an early remelting, probably by impacts, of the primary crust derived from the Martian mantle. Therefore, these igneous clasts can provide information about the ancient surface of Mars, allowing us to study the physicochemical conditions that existed on the planet’s surface, including the fugacity of oxygen at the time of the reshuffle. the crust. This information is essential to limit the timing of establishment of the hydrosphere and atmosphere of Mars and, therefore, the potential for early habitability, âthe authors explain.
Isotopes of titanium played a key role in the work. âThus, the combination of the chemical and isotopic compositions of Ti can be used to determine the thermal and / or redox magmatic histories of igneous rocks, in other words, the T–FO2 paths during the evolution of magma, âwrite the authors in their article.
It’s fine as far as it goes. But how did a cold planet like Mars conserve this water at a time when the Sun was much younger and weaker? How did this water get deposited in ancient lakes and rivers – and even in the oceans – of which we find evidence today?
According to the researchers, the same impact that released all that oxygen also released greenhouse gases. These gases have warmed the atmosphere enough for the liquid water to persist. According to Zhengbin Deng, “this means that the atmosphere rich in CO2 may have caused an increase in temperatures and thus allowed liquid water to exist on the surface of Mars.”
But there is a caveat to these results, and it comes from the authors themselves. ” The top ?17The O component of water at the start of Mars may represent either water supplied by impact materials such as water-rich asteroids, or, alternatively, water equilibrating with photochemicals from the water. primitive Martian atmosphere. Our data cannot distinguish between these two possibilities.
But that doesn’t mean their data is downright weak. “Nevertheless, an impact origin for basaltic clasts NWA 7533/7034 is established from their enrichment in highly siderophilic elements.
A theory is rarely confirmed or disproved on the back of a single study. This one is no exception. But it does point to another recent study examining 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 water itself, but hydrogen and oxygen that got locked in the mantle of the planet. Over time, these elements have combined into water. If this study is correct, the hydrogen and oxygen in Mars’ mantle may also have combined to form water through violent impacts long before asteroids and other bodies delivered it. .
Or it may be that the water on Earth and the water on Mars have multiple sources. It can come from both asteroid impacts and the solar nebula.
It seems there is a possibility that the rocky planets will have water sooner than not, and asteroid delivery is not necessary. In any case, the conversation about the source of water on the rocky planets has become more interesting.