Rocky planets like Earth formed from the aggregation of millions of small bodies. Some of its current features were sculpted by the final collision of planetary embryos, bodies similar to the larger asteroids we know today, such as Ceres and Vesta.
Therefore, EarthS past was marked by partially dehydrated materials, subjected to the high temperatures and pressures inherent to their size and the gigantic collisions they suffered.
So, considering the essential role that water plays on our planet – not only in the atmosphere and hydrosphere, but also in the Earth’s crust and mantle – the question arises: where does it come from?
Formation of the Earth: the constituent elements
To delve deeper into these primordial processes, we have isotopes: some chemical elements have different numbers of neutrons in their nuclei, which slightly changes their atomic mass and properties.
In fact, the composition of the rocks that make up the Earth presents the three known varieties of oxygen: O, O and O. These three isotopes participate decisively in the formation of rocks, be they basalts, granites or schists, to give some examples of those that dominate our planet. The oxygen isotope ratios in these terrestrial rocks they reveal a direct connection to asteroids associated with ordinary chondritic meteorites or a mineral called enstatiteindicating that such bodies were in the majority as building blocks of our planet.
however,such asteroids are usually characterized by having formed at high temperatures. As a result, they lost much of the water that, in some cases, we know they contained.The mystery remains about the origin of terrestrial HO.
Heavy hydrogen or deuterium as an answer
In the discipline of cosmochemistry it is indeed common to compare the water in our oceans with that stored in other bodies in the solar system. Hydrogen, the simplest atom, whose nucleus contains a proton, dominates Earth’s water. However, 1.5% of ocean water molecules contain a deuterium atom. And deuterium is a somewhat special hydrogen: it has a proton and a neutron, which give it a greater mass.
Without going into further detail, the key idea is that the proportions of deuterium in water could be conserved in external processes of water distribution to the Earth. At least it’s an approximation that can help us look for a connection with other objects in the solar system.
What comet 67P/Churyumov-Gerasimenko tells us
one of the flagship space missions of the European Space Agency (ESA) was Rosetta, dedicated to the exhaustive study and mapping of comet 67P/Churyumov-Gerasimenko. During the two years in which he followed the comet closely, he had the possibility to study it with cutting-edge instrumentation; The findings represented an unprecedented advance in our understanding of the nature, behavior and evolution of these icy objects.
Comets are a porous amalgam of small mineral particles, ice and organic matter. In particular, water ice usually dominates, which when heated sublimates and becomes part of the comet’s coma.
Pioneering studies conducted in 2014 to determine the percentage of deuterium in 67P/Churyumov-Gerasimenko revealed a surprise: A higher concentration of deuterium was found than in any comet, about three times greater than that found in Earth’s oceans.. This seemed to indicate that perhaps this type of comet was not a panacea and could not have transported our planet’s water over the eons.
kathleen Mandt, one of the researchers on the Rosetta mission team, was intrigued by these unexpected results. This motivated her to recalibrate the observations by taking into account the effect that the presence of micrometric dust might have had on the previous study. After all, Rosetta was in the comet’s coma. The findings have just been published in Advances in science.
It was no easy task: Mandt used an advanced statistical computing technique to automate the laborious process of isolating deuterium-rich water in more than 4,000 measurements obtained by the Rosetta spacecraft in coma of gas and dust who was traveling at 67P/churyumov-Gerasimenko.
Consistent results
The fruit of these new calculations cannot leave us indifferent: apparently, Jupiter’s so-called family of comets may have considerably contributed to bringing water to Earth.
It is a storehouse of frozen bodies with an orbital period around the Sun of less than 20 years subject to the gravitational environment of that giant planet. even today
Well, these comets have a proportion of deuterium practically identical to that present in the water of the Earth’s oceans.
Measurements of isotopes contained in the water of various objects in the aolar system. The measurements are compared to VSMOW values on the ground (dashed lines). several species have been reported for comet rosetta 67P/Churyumov-Gerasimenko (67P/CG; open black diamonds with blue error bars) and are compared with the results of this work (open black squares with blue error bars). (A) Several D/H measurements are available for deuterium, including chondrites (gray), moons of Saturn (cyan and orange), two TNO trans-neptunian bodies (steel blue), and several Oort cloud comets (filled with blue ). ) and the Jupiter family (blue with black outline). (B) The 16O/17O oxygen isotope ratio is available for the Sun, Mars and chondrites (gray), the satellite Titan (orange), and the comet 67P/CG. (C) And the 16O/18O isotope ratio was also measured on Jupiter, Venus, several Oort Cloud comets (OCC; filled with blue), and an additional Jupiter-family comet (blue with black outline).
Mandt et al. (2024) Scientific advances
In any case, to know if there were other significant sources of HO, it will still be necessary to study some hydrated objects in the asteroid belt. This is the case of Ceres, whose water content even exceeds that of our planet, so we set it as the goal of a future space mission. Each mission to a hydrated asteroid will allow us to discover a new piece of that great puzzle.
How do isotopes help scientists understand the formation of planetary bodies?
Interview: Time.news Editor with Dr. Emily Hart, Expert in Planetary Formation
Time.news Editor: Welcome, Dr. Hart! We’re excited to have you with us today to discuss the fascinating origins of Earth and the role of water in it’s formation.
Dr. Emily Hart: Thank you! I’m thrilled to be here, especially since this topic is so dynamic and layered with mysteries.
Editor: Let’s dive right in. You mention that rocky planets like Earth formed from millions of small bodies colliding together. Can you elaborate on how these processes sculpted our planet?
Dr. Hart: Absolutely! Earth was formed from planetary embryos—essentially larger bodies that collided and fused. These collisions weren’t gentle; they were enormous impacts that generated significant heat and pressure, leading to the current geological features we see, such as mountain ranges and ocean basins. During this tumultuous time, materials were partially dehydrated, which is essential for understanding the planet’s evolution.
Editor: That’s intriguing! Water plays such a vital role on Earth, but it begs the question: where did all our water come from?
Dr. Hart: Exactly! The origin of Earth’s water is one of the key questions in planetary science. Many scientists believe that some of the water may have been delivered by icy bodies from the outer solar system, like comets.However, we also need to consider that the original building blocks—asteroidal materials—likely contained less water because they formed in hotter regions and lost much of it during formation.
Editor: Speaking of asteroids, you mentioned isotopes of oxygen in your article. How do they help us trace the origins of Earth’s materials?
Dr. Hart: Great question! The three isotopes of oxygen found in terrestrial rocks help us connect those materials to specific types of asteroids, notably ordinary chondrites and enstatite. These isotopic ratios provide valuable facts about the temperature and conditions under which these materials formed, hinting at the potential sources of water and other elements on Earth.
Editor: I find the distinction of deuterium fascinating. How does this heavier hydrogen isotope contribute to our understanding of Earth’s water?
Dr. Hart: Deuterium is indeed crucial! While hydrogen dominates Earth’s water composition, the presence of deuterium—accounting for about 1.5% of ocean water molecules—suggests that the process through which water was delivered to Earth could have left specific signatures. By comparing deuterium ratios in Earth’s water with that in comets and other body types, we can establish potential connections and better understand where our water originated.
Editor: that leads us to Comet 67P/Churyumov-Gerasimenko, which was the subject of ESA’s Rosetta mission. What insights did it provide?
Dr. Hart: The Rosetta mission was groundbreaking! It provided an unprecedented look at comet 67P, revealing its structure as a porous mix of ice, mineral particles, and organic matter. The isotopic fingerprints of the water in the comet’s surface materials could offer clues about how similar bodies might have contributed to Earth’s water supply. It’s a puzzle where each piece—whether from asteroids or comets—helps us form a clearer picture of our planet’s origins.
Editor: It seems like we are just scratching the surface of understanding earth’s history! What excites you the most about this ongoing research?
Dr.Hart: The potential for revelation is vast! With advancements in technology and space exploration missions, we have the chance to unravel more layers of our solar system’s history. Each mission, like rosetta, helps us understand not just Earth, but the larger story of planetary formation and the conditions that sustain life. It’s about piecing together our cosmic history, which is as thrilling as it is profound.
Editor: Thank you, Dr. hart, for sharing your valuable insights today! The origins of our planet—and its water—are truly captivating, and we look forward to following the developments in this field.
Dr.Hart: Thank you for having me! It’s a pleasure to discuss these exciting topics with your audience.
