[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/7011\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EThe moon\u2019s water: where did it come from \u2013 and where did it all go?\u003C\/h2\u003E\u003Cp\u003EThe next time you take a sip of water, take a moment to consider where it has come from. It may have travelled from a local reservoir to your tap, while bottled water can come from springs in another country entirely.\u003C\/p\u003E\u003Cp\u003EBut new research suggests the water we drink and depend upon to sustain life here on Earth may have its origins in a far more distant place \u2013 outer space.\u003C\/p\u003E\u003Cp\u003ENew analysis of moon rock fragments brought back by Apollo astronauts in the 1960s and 1970s suggests much of the water on our planet was carried here by asteroids and comets that collided with the Earth shortly after it formed 4.54 billion years ago.\u003C\/p\u003E\u003Cp\u003EThe research, which uses modern techniques to look at the composition of chemical traces in the rocks, is also providing new evidence to support theories about how the Moon itself formed and how the traces of water found on its surface got there.\u003C\/p\u003E\u003Cp\u003E\u2018The moon is like a time capsule,\u2019 said Professor Fr\u00e9d\u00e9ric Moynier, a cosmochemist at the Institut de Physique du Globe de Paris, in France. \u2018Its rocks are far older than anything we can find here on Earth, so they hold a lot of valuable information.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EUnchanged\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EVolcanic activity and the continuous movement of tectonic plates have destroyed all of the oldest rocks here on Earth. The oldest to be found here, found in a few locations like Greenland, are just 3.8 billion years old.\u003C\/p\u003E\u003Cp\u003EThe moon\u2019s rocks, however, have remained largely unchanged since it formed 4.51 billion years ago. Hidden inside the minerals in the rocks are tiny quantities of chemicals such as zinc, potassium, copper, chromium and even water, which was also found to exist in \u003Ca href=\u0022https:\/\/www.pnas.org\/content\/115\/36\/8907\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Esmall frozen deposits in meteorite impact craters\u003C\/a\u003E on the lunar surface last year. These chemicals are known as volatiles due to their relatively low boiling points, which means they can evaporate from a planet\u2019s \u2013 or a moon\u2019s surface.\u003C\/p\u003E\u003Cp\u003EBy looking at the relative amounts of different isotopes of these volatiles in lunar rocks, scientists like Prof. Moynier have pieced together information about the moon\u2019s early history and compare this to what we find here on Earth.\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018The moon is like a time capsule.\u2019\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EProfessor Fr\u00e9d\u00e9ric Moynier, Institut de Physique du Globe de Paris, France\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp\u003EThese isotopes\u2019 ratios act like a fingerprint that can be used to match the source of the materials found on Earth and the moon. Dr Mahesh Anand, a reader in planetary science at The Open University in the UK and leader of a project called \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/rcn\/201255\/factsheet\/en\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003ERESOLVE\u003C\/a\u003E, has been using sophisticated spectroscopy techniques to study the volatile isotopes trapped inside crystals of a mineral called apatite in rocks brought back by the Apollo missions.\u003C\/p\u003E\u003Cp\u003EHe and his colleagues have then compared these to the isotopic compositions of volatiles here on Earth, along with those found on asteroids and comets, which have been obtained from meteorites found on Earth and interplanetary space missions to visit comets, such as the European Space Agency\u2019s recent Rosetta mission.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWater\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EThree years ago, Dr Anand was part of a study which proposed 80-90% of the water on Earth and the moon \u003Ca href=\u0022https:\/\/www.nature.com\/articles\/ncomms11684\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Ecame from an asteroid-like source\u003C\/a\u003E. \u2018Less than 10% came from a comet-like source,\u2019 he said.\u003C\/p\u003E\u003Cp\u003ELast year, he and his team \u003Ca href=\u0022http:\/\/advances.sciencemag.org\/content\/advances\/suppl\/2018\/03\/26\/4.3.eaao5928.DC1\/aao5928_SM.pdf\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Epublished further findings\u003C\/a\u003E based on high precision analysis of the oxygen isotopes found in rocks on the Earth and moon. They found only tiny differences between the isotopic properties on the two bodies. \u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u2018If the water had arrived after the moon had formed, the two would have had very different isotopic fingerprints,\u2019 said Dr Anand. \u2018It suggests that the Earth and the moon received water together at the same time.\u2019\u003C\/p\u003E\u003Cp\u003EThis points to a tantalising scenario \u2013 for a small body like the moon to have obtained the same isotopic composition suggests they may have been part of the same planet. It supports theories that a Mars-sized protoplanet called Theia crashed into Earth a little over 4.54 billion years ago, throwing out a shower or vapour and debris, which condensed to form our moon.\u003C\/p\u003E\u003Cp\u003EIf the Earth and moon formed in this giant impact after water had already arrived, as the findings by Dr Anand and other teams now suggest, the moon should have received a share of that water. Minute quantities of oxygen and hydrogen \u003Ca href=\u0022https:\/\/www.nature.com\/articles\/ngeo2173\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Etrapped inside rocks beneath the surface\u003C\/a\u003E suggest there was \u003Ca href=\u0022https:\/\/www.nature.com\/articles\/ngeo2845\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Eonce more water on the moon\u003C\/a\u003E than there is now. Recent unmanned missions to the moon have discovered a few remnants of water ice trapped in sheltered craters around the poles, but much of the moon\u2019s surface is now dry.\u003C\/p\u003E\u003Cp\u003ESo where did the moon\u0027s water go?\u003C\/p\u003E\u003Cp\u003EThis is where Prof. Moynier\u2019s work comes in. He is leading a project called \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/rcn\/193500\/factsheet\/en\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EPRISTINE\u003C\/a\u003E that aims to measure the isotopic levels of volatiles in lunar rock to learn what happened to the water on the moon.\u003C\/p\u003E\u003Cp\u003E\u2018The difference between the isotopes is weight as the atoms have different numbers of neutrons in the nucleus,\u2019 said Prof. Moynier. \u2018When you heat up volatiles like zinc, potassium and water, the isotopes behave in different ways. The lighter ones will turn to vapour more readily while the heavier ones will remain behind in the residue.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EProxies\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EBy looking at the ratio of heavy isotopes to light ones in more than 40 Apollo rock samples, Prof. Moynier and his team have pieced together some of the history of water and other volatiles on the moon.\u003C\/p\u003E\u003Cp\u003EThey have focused on solid volatiles like zinc and potassium because there are relatively higher concentrations of them in lunar rocks than water.\u003C\/p\u003E\u003Cp\u003E\u2018Water is so volatile that there is very little of it in lunar rocks, which makes it hard to detect in the small samples we are dealing with,\u2019 explained Prof. Moynier. \u2018So we can use other volatiles like zinc, potassium and copper as proxies that can tell us something about what happened to the water. Even so, there is 100 times less zinc in lunar rocks than those on Earth.\u2019\u003C\/p\u003E\u003Cp\u003EProf. Moynier and his colleagues found that as well as having far less chromium, zinc and other solid volatiles, the traces from the moon had different isotopic ratios compared to Earth - theirs had far more heavier isotopes.\u003C\/p\u003E\u003Cp\u003E\u2018It suggests that the moon got depleted in these volatile elements by evaporation at some point,\u2019 he said.\u003C\/p\u003E\u003Cp\u003EHe believes that rather than being lost in the giant impact that cleaved the moon from the Earth in the first place, it may have \u003Ca href=\u0022http:\/\/advances.sciencemag.org\/content\/3\/7\/e1700571.full\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Elost its water and other volatiles sometime later\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003EIt is thought that after the moon began to form following the giant impact, its surface remained molten for several million years. This magma ocean is thought to be what led to the distinctive light and dark areas, or mare, that are visible on the moon\u2019s surface.\u003C\/p\u003E\u003Cp\u003E\u2018As the isotope distribution depends on temperature, we can use it as a thermometer to tell us what happened,\u2019 said Prof. Moynier. He and his team have used chromium isotopes to calibrate what they were seeing in the lunar samples to temperature.\u003C\/p\u003E\u003Cp\u003EThey found the volatiles were not lost at the extremely high temperatures that would be expected in an event like a giant impact, but at \u003Ca href=\u0022https:\/\/www.pnas.org\/content\/115\/43\/10920.short?rss=1\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Elower temperatures of 1,200 degrees C\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003E\u003Cspan style=\u0022font-weight: normal !msorm;\u0022\u003E\u003Cstrong\u003EGravity\u003C\/strong\u003E\u003C\/span\u003E\u003C\/p\u003E\u003Cp\u003E\u2018This is exactly what the temperature of the magma ocean of the moon is supposed to be,\u2019 said Prof. Moynier. \u2018What we see is that the moon lost its volatiles not during the giant impact itself, but maybe a million or so years afterwards.\u003C\/p\u003E\u003Cp\u003E\u2018They evaporated off, but due to the gravity of the Earth, they probably then fell back onto the Earth. So some of our water and other volatiles have come from the moon. Not a lot, but some.\u2019\u003C\/p\u003E\u003Cp\u003EBut the story doesn\u2019t quite end there either. Dr Anand and his colleague Dr Ana \u010cernok, a geochemist at The Open University, have been studying the effect of meteoroid impacts on the isotopic compositions of volatiles in lunar rocks.\u003C\/p\u003E\u003Cp\u003EGathered from a variety of sites during NASA\u2019s Apollo 17 manned mission to the moon in 1972, the samples consist of surface rocks, cores drilled down below the surface, and material from impact craters.\u003C\/p\u003E\u003Cp\u003EThe two have been able to look for signs of shock in the apatite crystals that would have been caused by meteoroid impacts. They found that while some of the samples show significant signs of shock, the isotopic compositions remain largely unaffected.\u003C\/p\u003E\u003Cp\u003EThis suggests that the volatiles like water trapped inside these crystals have not been altered despite bombardment from meteorites on the moon. Other substances like uranium trapped inside the apatite crystals along with the water have also allowed them to date when they formed.\u003C\/p\u003E\u003Cp\u003EThe results still have to be published, but Dr Anand says they are finding ages that have never been recorded in lunar samples.\u003C\/p\u003E\u003Cp\u003E\u2018We are still trying to figure it out ourselves, but it seems to be pointing to a unique event in the geological history of the Earth-moon system.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research in this article was funded by the EU. 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