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EXPERT REACTION: Water on the moon! And it could help us head out to space

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Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Researchers have put forward more evidence for water on the Moon. Previous discoveries of hydration on our moon have been unable to differentiate between water and other combinations of hydrogen and oxygen. However observations through the SOFIA - a telescope in a 747 plane - have allowed scientists to detect the unique signature of H2O at the Moon’s high southern latitudes. Researchers have also measured the Moon’s permanently shadowed areas - ‘cold traps’ - which could trap water in areas as small as 1cm in diameter. The authors suggest cold traps could cover around 40,000km2 of the lunar surface. The findings indicate water is produced or delivered on the Moon by various processes, which may have implications for future lunar missions.

Journal/conference: Nature Astronomy

Link to research (DOI): 10.1038/s41550-020-01222-x

Organisation/s: University of Hawai'i at Mānoa, USA, University of Colorado, USA

Funder: Molecular water: Observations were made using the NASA/DLR SOFIA. SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA) under NASA contract number NNA17BF53C and the Deutsches SOFIA Insitut (DSI) under DLR contract number 50 OK 0901 to the University of Stuttgart. Cold traps: This study was supported by the Lunar Reconnaissance Orbiter project and NASA’s Solar System Exploration Research Virtual Institute. N.S. was in part supported by the NASA Solar System Exploration Research Virtual Institute Cooperative Agreement (NNH16ZDA001N) (TREX).

Media release

From: Springer Nature

The unambiguous detection of molecular water (H2O) on the Moon and areas on the Moon where water could be trapped stably are reported in two papers published this week in Nature Astronomy. These findings may have implications for future missions to the Moon.

Previous research has reported signs of hydration on the lunar surface, particularly around the south pole. However, these detections are based on a spectral signature, at 3 µm, that cannot discriminate between H2O and hydroxyl bound in minerals.

In one paper, Casey Honniball and colleagues analysed data from the Stratospheric Observatory for Infrared Astronomy (SOFIA) airborne telescope that observed the Moon at 6 µm. At this wavelength, they were able to detect a spectral signature of H2O that is not shared with other hydroxyl compounds. They found that water is present at high southern latitudes in abundances around 100 to 400 parts per million H2O. The authors suggest that the detected water is probably stored in glass or between grains on the lunar surface that protect it from the harsh environment.

In another study, Paul Hayne and colleagues examined the distribution of permanently shadowed areas — known as cold traps — where water could be captured and remain permanently. The authors assessed a whole range of possible sizes for cold traps, down to 1 centimetre in diameter. They found that small scale ‘micro’ cold traps are hundreds to thousands of times more numerous than larger cold traps, and they can be found at both poles. The authors suggest that approximately 40,000 km2 of the lunar surface has the capacity to trap water.

These findings indicate that water is efficiently produced or delivered on the Moon by various processes, and is likely to be stored in the Moon’s cold traps at both polar regions. The presence of water may have implications for future lunar missions targeting and accessing these potential ice reservoirs.


  • Springer Nature
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    "Molecular water detected on the sunlit Moon by SOFIA" - URL will go live after the embargo ends
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    "Micro cold traps on the Moon" - URL will go live after the embargo ends

Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Kim Ellis Hayes is a Scientist Astronaut Candidate, Senior Lecturer Space Law & Research, and Director of Earth Space Tech, an Adjunct Faculty for the International Space University

The confirmation that water exists on the moon in larger quantities than previously estimated provides commercial space businesses with the data which will boost private investment. In-situ water is an essential component for generating life resources for life support, fuel production, and in-situ resource utilisation to support an ongoing human presence on the lunar surface.  

The Outer Space Treaty outlines rules for peaceful operations in outer space, celestial bodies and the Moon. The treaty outlines rules which promote sharing of resources like water to ensure these materials are available to everyone.

Last updated: 11 Nov 2020 6:00pm
Declared conflicts of interest:
None declared.
Dr Themiya Nanayakkara is an astronomer at Swinburne University of Technology studying the early Universe and he is the Australian point of contact for the James Webb Space Telescope user support.

Given our understanding of how life forms and evolves, we think that water is an essential component that is required to harbour life on planets. There have been subtle hints that our Moon may contain water, but earlier observations that targeted a 3µm feature couldn’t distinguish whether the lines they saw in the spectra were due to molecular water or hydroxyl, a group we find loaded in alcohols and sugars.

Honniball and collaborators have now targeted a much higher wavelength feature at 6µm using data from the SOFIA observatory, which is a modified Boeing 747 aircraft with a massive hole fitting a 2.5-meter mirror (our atmosphere absorbs most parts of the infra-red wavelengths, so to observe we need to either put telescopes in space or fly an aircraft with a telescope in it at an altitude of 12km or higher). They find spectral signatures that can only be explained by molecular water on the Moon. They put forward many theories for the origin of the water, but from the results, it is still hard to distinguish if the water is within glasses, grains, or in void spaces.

Hayne and collaborators also make an interesting discovery about the Moon and find that there is a larger possibility for it to form ice in regions identified as cold traps. These are permanent shadow regions in the moon and can be small as 1cm covering a total of ~40,000 square kilometres of the moon’s surface. So, they suggest that future moon missions targeting the polar regions where cold traps are numerous may be able to access these ice reservoirs, which might be helpful for future human explorations of the moon.

Last updated: 27 Oct 2020 11:45am
Declared conflicts of interest:
None declared.
Professor Fred Watson, AM is an Astronomer-at-Large from the Department of Industry, Science, Energy and Resources

We have known for more than a decade that the Moon’s polar regions contain oxygen and hydrogen atoms bonded together either as hydroxyl (OH) or water (H2O). Their presence was revealed by spacecraft observations that were unable to distinguish between the two molecules, but many scientists assumed that water was likely to be the dominant component. Deep polar craters that never feel the heat of the Sun can have temperatures as low as -250ºC, and were thought to be traps for water ice delivered perhaps by impacting comets.

Now these assumptions have received strong support from observations made with NASA’s jumbo-jet Stratospheric Observatory for Infrared Astronomy (SOFIA). High concentrations of water have been unambiguously detected, and are thought to be contained either in glassy minerals on the lunar surface, or trapped as ice in voids between grains of lunar soil. Either way, the possibility of water reservoirs on the Moon is of great interest in upcoming lunar exploration missions, adding to the intrigue of this exciting discovery.

Last updated: 26 Oct 2020 4:55pm
Declared conflicts of interest:
None declared.
Dr Nick Tothill is a Senior Lecturer in Physics at Western Sydney University

We thought we could see water ice on the Moon, but there were lingering uncertainties - were we being too optimistic? This question has now been answered - there really is water ice on the Moon, even on the hot daylight side. The problem was that the water ice signature that was found before was really just telling us that there were oxygen and hydrogen atoms bound together. On the Earth, this is mainly water, but on the Moon, you can't be so sure.

In this work, a different signature was used, one that only arises from two hydrogen atoms bound to an oxygen atom - a water molecule. All of these signatures are found in the infrared spectrum, which makes them hard to do from the surface of the earth, because we're sitting under a blanket of water in the atmosphere, so we can't see the tiny water signals from outside. That's why the original observations that suggested water were done by spacecraft, and the new observations that confirm it have been done by an infrared telescope flying high above all our water clouds in a converted 747.

A problem with this new work, though, is that it can't tell us much about how much there might be and where to look for it, which are vital concerns for future lunar exploration. Paul Hayne and his collaborators have built models of where the permanent shadows are likely to be - these permanent shadows (or cold traps) capture water vapour and freeze it out into ice. 

Taken together, these papers tell us that there really is water ice on the moon, and it's probably widespread over both polar regions - with a bit more in the south. This in turn tells us how and where to look for water on the moon, with either robot or human explorers.

Last updated: 26 Oct 2020 1:08pm
Declared conflicts of interest:
None declared.
Dr Rebecca Allen is the project coordinator for Swinburne's Space office, coordinator of Swinburne Astronomy online and manager of Swinburne Astronomy productions

Astronomers have long thought there was water on the Moon, but until now they have not been able to confirm it's in the form we think of, molecular water or H2O. This is because previous measurements could not distinguish whether the water was present as ice or locked away in minerals called hydroxyls. The team who led the discovery used an instrument on the SOFIA telescope to probe longer wavelengths of light that revealed a signature only water in its molecular form would create. 
With a confirmation of molecular water, the next big question the team addressed was how much of it and where. A nice result was that a large amount of the water is in the form of glass, created as small meteors collided with hydroxyls on the Moon’s surface. By carefully measuring where there is more of the water-rich compounds, the team could determine (and confirm) that the majority of the Moon’s water likely resides at its poles, with the south pole containing the majority. 
Finally, the team revealed there might be a lot more places to find water in ice form through the presence of many locations called micro cold traps. These are areas where the Moon’s surface is permanently shadowed and the conditions are right for ice to exist. These traps can be many kilometres in size or just a few centimetres, formed through craters and smaller features on the Moon’s dynamic landscape. 
These are critical findings for future space exploration missions which plan to utilise the Moon’s water to create fuel and other resources.

Last updated: 26 Oct 2020 12:54pm
Declared conflicts of interest:
None declared.
Associate Professor Alice Gorman is from the College of the Arts, Humanities and Social Sciences at Flinders University and an internationally recognised leader in the emerging field of space archaeology

These new results confirm something that we didn’t know for sure:  the Moon has actual water and not just various other oxygen/hydrogen compounds. Water occurs frozen in large craters in the permanently shadowed regions of the South Pole, but it’s also present in a multitude of small craters, down to 1 cm in size – smaller than an ice cube. And it’s likely that this water is fairly recent.

The lowland area of Mare Serenitatis is also showing a distinct water signal. Mare Serenitatis is where the Israeli Beresheet lander crashed in 2019. Thousands of dried tardigrades were secretly sent on this mission. These hardy 1.5 mm creatures can survive in space and are revived by water. But we don’t have to worry that tardigrades are now running around the Moon. They’re encased in resin, and the water is most likely trapped inside glasses formed by micrometeorite impacts. 

The Apollo 17 mission brought back samples of this glass from a valley on the edge of Mare Serenitatis in 1972. Around the landing site, the crew observed small craters with glassy material at the bottom.

These results have implications for how humans might extract water to sustain a habitation or make fuel. Extraction from small craters might be less technically demanding than mining the big ice craters, but it may also be more destructive to a unique landscape of shadows and ice. Permanently shadowed regions only occur on the Moon, Mercury and the dwarf planet Ceres.

As we learn more about the lunar water cycle, it seems that water might be a renewable resource. This is a new challenge for sustainable environment management on the Moon.

Last updated: 26 Oct 2020 12:50pm
Declared conflicts of interest:
None declared.
Dr Jasmina Lazendic-Galloway is a lecturer in the School of Physics and Astronomy at Monash University

The paper by Honniball et al. reports detection of water on the Moon with SOFIA infrared observatory.  This water might be brought by meteorites that bombard the surface of the Moon, or more likely originate from the Moon’s regolith itself. Either way, the impact by meteorites seems to be forming pockets within the impact melt where water gets trapped. This detection points to a localised detection, rather than being a general property of the lunar surface, as compared to the LRO water detection in polar regions by Li et al. in 2018.

The paper by Hayne et al. reports on the estimation of how many permanently shadowed regions on the Moon have conditions to hold water ice, on larger scales of 1 km but also down to tiny scales of 1 cm. They found that these regions can hold a significant amount of water ice on the surface of the Moon, much higher than predicted previously, but also not uniformly distributed.

Both discoveries are very exciting in terms of promise for the Moon to provide water resources for future human space exploration.

Last updated: 26 Oct 2020 12:48pm
Declared conflicts of interest:
None declared.
Dr Ben Montet is a Scientia Lecturer in the School of Physics at UNSW

This work confirms previous analyses (1) that demonstrate clear evidence for water at the lunar poles. However, we haven’t found a fountain or lake on the moon, the water density is very low, it is confined to the poles, and is likely trapped in glasses or rocks on the surface.

This would provide challenges for a short-term crewed mission like the Apollo missions to access this water quickly and in sufficient quantities to meet the demands of a human crew.

Future extended lunar missions, like a permanent moon base, may be able to bring equipment to access this water, but they will need to be careful to conserve this precious resource, even more so than on Earth given its likely limited extent.

Scientifically, understanding in detail the lunar water content, how this water is delivered to the Moon, and how quickly it is replenished will help us better understand the processes that delivered water to the Earth in the early Solar System, allowing us to form and retain oceans to the present day.


Last updated: 26 Oct 2020 12:34pm
Declared conflicts of interest:
None declared.
Dr Brad Tucker is a Research Fellow and Outreach Manager at Mt. Stromlo Observatory at the Australian National University

Water is a key resource for future space exploration. Not only can water be used to support humans, but it also can be used for fuel. Water is the key for the new Moon race. This discovery shows how common water is on the Moon - both how much and where.  This will be key for mapping future human missions and the infrastructure on the Moon.

Last updated: 26 Oct 2020 12:32pm
Declared conflicts of interest:
None declared.
Dr Jonti Horner is a Vice-Chancellor's Senior Research Fellow at the University of Southern Queensland

This is definitely exciting news!

We've long suspected that the polar regions of the Moon could well host water ice, potentially in relatively large amounts. To have the presence of water ice on the Moon confirmed, though, is really exciting - and justifies the interest that many countries have in visiting, and even building bases at, the lunar south pole.

Similarly, the work on 'cold traps' on the Moon is fascinating, as to me it suggests that the amount of the lunar polar regions that could play host to water ice might be greater than previously thought - which will doubtless be a great boon for future lunar exploration.

To illustrate how important these findings are, it is worth noting that the US 'Artemis' program, which aims to return humans to the Moon by 2024, includes a plan for a permanent base at the Moon's south pole. The suspected presence of water at the Moon's south pole has played a major role in its selection as the best location for 'Artemis Base Camp', and I'm sure that people working towards that project are thrilled to see these results, confirming that there really is water there for them to make use of.

It might even be that future missions to the Moon's south pole will be built to be refueled on arrival at the Base Camp, using the Moon's water to directly lower the costs in travelling to and from our nearest neighbour!

Last updated: 23 Oct 2020 5:22pm
Declared conflicts of interest:
None declared.
Alan Gilmore, retired Superintendent of the University of Canterbury's Mt John Observatory

It has long been expected that water ice would be found in craters near the Moon's poles where the crater floors are always in darkness. The water would have been delivered to the Moon over millennia by comets and icy asteroids colliding with the Moon. Any water vapour released would freeze onto the cold dark surfaces. The new results extend the range of cold places to shaded areas on rough surfaces near the poles. They also suggest that water may be derived from chemical processes on the Moon's surface where hydroxyl molecules in lunar soils combine with hydrogen from the solar wind. 

Detection of the 6-micron infra-red signature of water ice, observed from the Stratospheric Observatory for Infrared Astronomy (SOFIA) airborne telescope, appears to confirm the presence of large areas of water ice near the Moon's poles. The ice will be a valuable resource for any long-term human base on the Moon. Putting such a base in a shaded crater near a pole would protect it from the extreme temperature fluctuations between lunar day and night. It would also provide some protection from solar cosmic rays, high energy particles radiated by the Sun. Having water ice nearby, albeit in low concentrations, would be an advantage.

Last updated: 23 Oct 2020 2:21pm
Declared conflicts of interest:
No conflict of interest.
Professor Andrew Dempster is Director of the Australian Centre for Space Engineering Research (ACSER) at UNSW Sydney

The two new contributions on moon water are important in different ways but each shows that water is more abundant on the moon than we may earlier have thought. Whereas before we saw signatures that "might" be water, that has now been confirmed as definitely water. In some ways this is lucky, because NASA, ESA and China have all committed significant funding to projects that assume the presence of water on the moon.

The second result shows that there are more 'cold traps' than earlier considered, where water ice can exist, so water is probably more widespread than once thought. Both these results are useful for Australia's $150million Moon to Mars program, and support Australia's recent signing of the Artemis Accords. We can now be more confident that applying Australia's resource extraction technology in space will have genuinely useful 'ore' to extract.

Last updated: 23 Oct 2020 12:44pm
Declared conflicts of interest:
None declared.
Swinburne University’s Professor Alan Duffy, Lead Scientist of The Royal Institution of Australia

Water on the Moon is more than just an exciting scientific discovery, it makes possible the future expansion of humanity into an multi-planet species!

To launch a litre bottle of water from Earth to the Moon costs $35,000 – almost the same cost as if we just made that bottle solid gold. But by accessing it directly from the Moon itself we turn our celestial neighbour into a resupply as well as a refuelling station.
Water can directly support astronauts on a planned Moon-base, used to grow food on long-duration missions to Mars, and even split into literal rocket fuel for powering our satellites and rockets across the Solar System.
The Moon was once thought to be a desert, devoid of water, but in just the last few years we’ve seen hints of it either locked away inside minerals / impact glasses or as hydroxyls (water missing the extra hydrogen) but now this measurement of between 100 to 400 parts per million of molecular water seems to be solid enough to drink. It might be a bit of a dusty drink as the water molecules are likely sheltered within or between tiny lunar grains. To fill a litre bottle with Moon water you’d need about ten tonnes of lunar soil, or regolith, so it still makes the Sahara look waterlogged by comparison.
That this measurement was made from SOFIA - an infrared telescope looking out the side of a converted 747 jet flying a dozen kilometres high in our atmosphere, just makes the discovery all the more incredible.
The water might lie in numerous, permanently shadowed holes pitted throughout the Lunar surface known as called ‘cold-traps’ as revealed by modelling of images from the Lunar Reconnaissance Orbiter. These cold-traps range from tiny, hair-width sized gaps to 1km across or more, covering 40 000 square kilometres of the Moon’s surface although the South Pole seems to have the most potential water sites.
If water is the oil of space, the Moon just became the OPEC of orbital refuelling.

Last updated: 23 Oct 2020 12:26pm
Declared conflicts of interest:
None declared.
Dr Craig Lindley is Project Leader for Geomodelling for Space Resources at Data61, CSIRO. He is currently running a project that is developing technology for mapping water ice and other minerals on the surface of the Moon as part of CSIRO's Space Technology Future Science Platform.

Water on the surface of the Moon can be used for several very important things, such as sustaining astronauts, creating oxygen and hydrogen for rocket fuel or power generation, or conducting horticulture experiments.

There’s intense international interest in finding and using water from the surface of the Moon, since the current cost of launching water from the Earth to the Moon is more than $1 million per litre.
These new studies are very important and exciting since they finally show that there really is molecular water on the Moon. We can now map where the water is on the surface, making it much less risky to undertake missions to reach it. We also now better understand how to build technology to extract the water.
There are still many things that we don’t know and it will take surface landers and sample returns missions to answer questions such as whether the water is trapped in glass or if it’s in protected voids in the lunar dust, dirt and rocks. This will make a big difference in the methods needed to extract and concentrate the water.
We also don’t yet know how water is distributed under the surface and there could be lots more where our sensors have not yet been able to reach.
Australia has exciting opportunities to participate in these ongoing missions and already has people developing some of the needed technologies in industry, at universities and in CSIRO, including CSIRO’s new Space Technology Future Science Platform.

Last updated: 23 Oct 2020 12:25pm
Declared conflicts of interest:
None declared.
Richard de Grijs is Professor of Astrophysics at Macquarie University and Associate Dean responsible for the global engagement of its Faculty of Science and Engineering.

It had long been suspected but firm evidence remained elusive—until now. For the first time, molecular water has been confirmed beyond any reasonable doubt near the Moon’s South Pole. It required observations with the SOFIA airborne telescope—at the high altitudes where infrared observations are largely unimpeded by water vapour in the Earth’s atmosphere—to obtain uncontested evidence of widespread water ice deposits on the lunar surface.

However, don’t expect to find hidden glaciers or ice caps. We’re talking about minuscule water ice grains contained in glassy beads which were most likely formed through the continuous bombardment of the Moon’s surface by micro-meteorites. Those impacts may have led to fairly efficient conversion of hydroxyl (OH) to molecular water (H2O); it is unlikely that the meteorites themselves are responsible for delivering the observed water deposits from outer space to the Moon's surface.

But don’t get too excited as yet; mining water on the Moon still has a long way to go before we can even think of basing ourselves in the harsh lunar environment and relying on the Moon’s natural resources for our survival. 

And while the authors suggest a widespread presence of water ice, at least in the polar regions, only 20 per cent of their signal reaches a level (“4 sigma”) that makes me confident that their detections are real; the remainder, at the “2 sigma” confidence level, could still mostly be enhanced noise in their data.

Nevertheless, a second paper published in Nature Astronomy this week—and based on a completely different data set—actually supports the SOFIA paper’s main implications. That should give us more confidence regarding the validity of the conclusions of both papers.

Last updated: 23 Oct 2020 12:24pm
Declared conflicts of interest:
None declared.

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