\ud83c\udf18Subscribe to 404 Media to get The Abstract, our newsletter about the most exciting and mind-boggling science news and studies of the week. For decades, scientists have puzzled over the \u201cdensity deficit\u201d in Earth\u2019s core, an unexplained discrepancy between the expected density of a solid iron core and the much lower density that is actually observed through seismic measurements of our planet\u2019s center.Now, scientists have provided some of the best experimental evidence yet that this deficit can be explained by vast oceans of hydrogen that are locked within the core, significantly lowering its overall density, according to a study published on Tuesday in Nature Communications.\u00a0\u00a0In addition to constraining this longstanding problem, the research reveals new insights about another persistent mystery: the original source of Earth\u2019s liquid water, the key ingredient that enabled life on our planet to emerge.\u201cHydrogen has long been considered a major light-element candidate to account for the observed density deficit in Earth\u2019s core,\u201d said researchers led by Dongyang Huang, an assistant professor of Earth and space sciences at Peking University, in the new study. \u201cFor decades, however, our knowledge of the exact content of H in planetary cores has been hindered by the inability to unambiguously quantify H in high-pressure samples.\u201dTo solve this problem, the researchers performed a series of experiments that simulated the extreme environment in the core during Earth\u2019s formation billions of years ago. This approach involved heating up iron metal with lasers to a fully-molten state that resembles ancient Earth\u2019s inner magma ocean, which reached temperatures up to 8,700\u00b0F, and pressures more than a million times more intense than those we experience on Earth\u2019s surface.\u00a0The team then searched for the presence of hydrogen in nanostructures made primarily of silicon and oxygen. The results revealed that the core\u2019s hydrogen percentage sits between 0.07 to 0.36 percent, which works out to roughly nine-to-45 times the amount of the hydrogen in all of Earth\u2019s oceans.But perhaps the most tantalizing part of the study is its implications for understanding the enigmatic origins of Earth\u2019s water, the wellspring of life on our world.Some theories suggest that Earth\u2019s water was primarily delivered from extraterrestrial sources, such as comets and asteroids that impacted our planet as it was forming more than four billion years ago. An alternate possibility is that Earth\u2019s water was largely sourced from its building blocks, including vast interior reservoirs of hydrogen. This latter scenario is supported by the new study.\u201cAlthough 71 percent of the Earth\u2019s surface is covered by ocean, mainly made of H, it has been argued that the majority of Earth\u2019s H had been stored in the core since its formation, ~4.5 billion years ago,\u201d the researchers said.The estimates presented in the study \u201crequire the Earth to obtain the majority of its water from the main stages of terrestrial accretion, instead of through comets during late addition,\u201d the team concluded.The study certainly helps tackle the mystery of the precise contents of Earth\u2019s core, though the authors note that their estimate has large uncertainties that will need to be further narrowed down in future work. They also suggest that hydrogen alone cannot explain the density deficit, and that other light elements or compounds, including water, might be contributing to the discrepancy.\u201cCompared to existing models for Earth\u2019s core composition this is a somewhat less H-rich core, and requires its density deficit to be accounted for by a mixture of light elements, rather than a single light species, akin to that of Mars\u2019 core,\u201d the team said in the study.Given that water is essential to all life on Earth, solving the riddle of its origins is the first step to understanding how our planet came to be inhabited, and whether other planets may commonly go through the same process.\u00a0\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"