If you asked someone who was reasonably knowledgeable about science how the earth got its water, they would likely tell you that it came from asteroids – or maybe comets and planetesimals – that crashed on our planet in the early days . There are details, nuances, and uncertainties about this idea, but it is widely believed that this is the most likely reason the earth has so much water.
However, there is a new explanation for the water of the earth. It is said that the water will come along for the journey when the earth has formed from the solar mist.
If that's correct, it means that most rocky planets could have water for at least part of their lives.
A new paper provides evidence that water is not being delivered to rocky planets, but is forming itself as part of the planetary formation process. The title of the paper 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 at the Globe Institute at the University of Copenhagen. The study was published in the journal Science Advances.
“There are two hypotheses about the origin of water. On the one hand, planets inadvertently come into play 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 is created in connection with the formation of the planet. Our study suggests that this hypothesis is correct, and if so, it is extremely exciting, since the presence of water is a bioproduct of the planet formation process, ”explains Martin Bizzarro.
The evidence for this hypothesis comes from a small meteorite called Black Beauty. Black Beauty (also known as Northwest Africa 7034) is a piece of Mars that fell to Earth and was discovered in the Sahara in 2011. It was mysterious because it defied categorization. Eventually, scientists discovered that it was a new classification of Martian meteorites, which they referred to as "Mars (basalt breccia)".
Mars Meteorite – NWA 7034 http://www.nasa.gov/mission_pages/mars/news/mars20130103.html The Mars meteorite called "Black Beauty" (Northwest Africa (NWA) 7034) weighs approximately 320 grams (11 ounces ). . Photo credit: NASA
Black Beauty is really old; According to this study, components of this are 4.45 billion years old. It is the second oldest Martian meteorite ever found. It is so old that it comes from the original Martian crust. But Black Beauty also has the highest water content of all Martian meteorites.
According to these studies, Mars had water for the first 90 million years of its existence. That way, asteroids had enough time to bomb the planet and provide water. The water must have another source.
Black Beauty forced scientists to ask a question: If the water of Mars – and with it the water of Earth – was supplied by collisions with aquatic bodies such as asteroids, how did the planets have water for the first 90 million years? Asteroids just didn't have enough time to deliver the water.
The researchers believe that the Black Beauty meteorite originated in the southern hemisphere of Mars. Photo credit: USGS / University of Copenhagen
“It suggests that water was formed with the formation of Mars. And it tells us that water can occur naturally on planets and doesn't need an external source like water-rich asteroids, ”he says.
The researchers received around 50 grams of Black Beauty for this study and developed a new method to unlock the secrets of the meteorite. They took 15 grams of it and crushed it, dissolved it and then analyzed it.
The analysis revealed something shocking. Although impactors did not provide this water, they did provide evidence of the source of this water.
Asteroid impacts on Mars may not have been the planet's water source. Photo credit: geol.umd.edu
“We developed a new technique that tells us that Mars suffered one or more severe asteroid impacts in its infancy. The impact, according to 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, ”said Zhengbin Deng.
Much of the evidence in this study relates to oxygen. Oxygen is a swinger; it can be combined with almost anything. In combination with other elements on Mars, the resulting minerals carry traces of their origin as isotopes. By tracking the origins of compounds containing elements such as iron and titanium, researchers developed a kind of timeline for the evolution of Martian rocks as they melted and solidified.
This research focused on 15 magmatic clasts of Black Beauty. The team performed a detailed analysis of these clasts using several types of spectroscopy.
“It has been suggested that these clasts are the product of early remelting of the primary crust from the Martian mantle, likely by impact. Hence, these magmatic clasts can provide glimpses of the ancient Martian surface and allow us to study the physicochemical conditions on the planet's surface, including oxygen volatility at the time of the crust overwork. This information is of crucial importance in order to limit the point in time of the establishment of the hydrosphere and atmosphere of Mars and thus the potential for early habitability, ”the authors explain.
Titanium isotopes played a key role in the work. “Thus, the combination of chemical and Ti isotopic compositions can be used to determine the igneous heat and / or redox history of igneous rocks, ie the T-fO2 paths during magma evolution,” the authors write in their paper.
As far as possible, that's fine. But how did a cold planet like Mars hold this water at a time when the sun was much younger and weaker? How was this water deposited in the ancient lakes and rivers – and even the oceans – of which we find evidence today?
According to the researchers, the same impact that released all of the oxygen released greenhouse gases as well. These gases heated the atmosphere enough that liquid water persisted. According to Zhengbin Deng, this means that the CO2-rich atmosphere may have caused a rise in temperature and thus liquid water was present on the surface of Mars.
The artistic impression of a warm, humid early Mars. This new research suggests that impacts may have released greenhouse gases that enabled the planet to retain liquid water on its surface. Image credit: Daein Ballard. CC-BY-SA-3.0
However, these results include a warning that was provided by the authors themselves. “The high-17O water component on early Mars can either represent water that is delivered by impact with material such as water-rich asteroid bodies, or alternatively water that is balanced with photochemical products from the early Martian atmosphere. Our data cannot distinguish between these two possibilities. "
However, that doesn't mean their data are weak overall. “An origin of influence for the basalt clasts NWA 7533/7034 results from their accumulation in highly siderophiles
A theory that has been confirmed or refuted on the back of a single study is rare. This one is no exception. However, another current study is presented in which the origin of the earth water is examined.
The earth is now a warm, watery wonderland. Perhaps more rocky planets started like this but eventually lost theirs. Photo credit: NASA Earth Observatory.
This latest 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 trapped in the earth's mantle. In the course of time these elements combined to form water. Also, if this study is correct, hydrogen and oxygen in the Martian mantle may have combined to form water from violent jolts long before asteroids and other bodies could have delivered it.
Or it could be that the waters of Earth and Mars had multiple sources. It can come from both asteroid impacts and solar nebula.
Chances are that rocky planets often have early water and that delivery by asteroids is not required. In any case, the conversation about the water source on rocky planets became even more interesting.