Cool discovery: new studies confirm Moon has icy poles

NASA

Andrew Dempster, UNSW

Water is more abundant on the Moon than we might have suspected, according to two papers published today in Nature Astronomy that confirm the presence of ice on and near the lunar surface.

It’s a boost for the prospect of extracting water from the Moon, which can help support humans, or be converted to rocket fuel, although the situation is far from simple.

The first paper, led by Casey Honniball of the University of Hawai'i, offers confirmation of the suspected discovery of water on the Moon. In previous studies, researchers had examined frequencies of absorbed radiation and identified the presence of chemicals called hydroxyl ions on the Moon.

Hydroxyl ions (OH-) are part of the water molecule H₂0, meaning water ice was a likely, but not definite, source of the hydroxyls detected. But as hydroxyl ions are found in many other compounds too, it was impossible to be sure.

The new research used a new technique and has shown that a significant proportion of those hydroxyls are indeed found within water ice molecules, possibly bound or suspended in the Moon’s surface rocks. More research is needed to deduce the precise details, but the presence of molecular water is big news.

The second paper, led by Paul Hayne of the University of Colorado, notes there are likely to be more “cold traps” containing water ice than previously estimated.

A “cold trap” is a place in permanent shadow, where ice can survive because it never receives direct sunlight, and where the temperature stays sufficiently low. Elsewhere, sunlight warms the ice, causing it to “sublime”: the Moon’s low atmospheric pressure means solid ice directly transforms into water vapour, which may refreeze somewhere else.

The study showed that at high latitudes, there were potentially very high numbers of these cold traps (possibly billions), some as small as 1cm across.

Images revealing shadows on the lunar surface, at a range of different scales. Hayne et al./Nature Astronomy

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Read more: Blowin' in the (solar) wind: how the moon got its water

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How much water is on the Moon? Current estimates, based on the previous detection of hydroxyls, range from 100 million tonnes to the more recent 2.9 billion tonnes. According to the new estimate, up to 30% of some areas of the lunar surface could be ice in cold traps.

Even using the conservative price for water offered by launch company ELA of $US3,000 per kg for delivery to low Earth orbit, the water on the Moon could be worth billions of dollars a year, because water can be split into hydrogen and oxygen and used as rocket fuel. Some of our research shows how a business case can be made at low Earth orbit.

The importance of the new findings is there is now far more certainty that the water is there, and there are more widespread opportunities to find it.

Good news for ice miners?

It’s a timely discovery, because there has been a lot of activity recently, including in Australia, developing projects to extract water on the Moon. In the past two weeks alone, NASA has let a contract for an ice-mining drill, and announced the launch aboard NASA’s Space launch System (SLS), designed for deep space missions, of three small satellites looking for water. Meanwhile, the European and Chinese space agencies have announced missions to explore the lunar south pole for water.

Australia is in this game because of the Australian Space Agency’s A$150 million commitment to the Moon to Mars program. Australia also this month signed the Artemis Accords, a series of bilateral agreements between the United States and other partners to develop a legal framework for space resources.

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Read more: Artemis Accords: why many countries are refusing to sign Moon exploration agreement

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That may sound like great news but Australia is also a signatory of the Moon Agreement, the UN’s approach to peaceful uses of the Moon and other bodies. Some say this is inconsistent with the Artemis Accords. We have called for the Australian Space Agency to provide clarity on this issue, and hosted events to discuss it (including a solid 1.5-hour debate).

Yet Australia is now a signatory to both agreements, with no explanation as to how that is possible under international law. We need the Australian Space Agency to provide clarity about its interpretation of both instruments, as soon as possible. The urgency for this action is pressing — we are now much more certain there is water to extract on the Moon, and that the barriers to entry have been lowered. Australian companies are building capability in space resources and they need certainty to allow those businesses to grow.

Andrew Dempster, Director, Australian Centre for Space Engineering Research; Professor, School of Electrical Engineering and Telecommunications, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Mars: mounting evidence for subglacial lakes, but could they really host life?

There seems to be a network of underground bodies of liquid water at Mars’ south pole. NASA/JPL/Malin Space Science Systems

David Rothery, The Open University

Venus may harbour life some 50km above its surface, we learned a couple of weeks ago. Now a new paper, published in Nature Astronomy, reveals that the best place for life on Mars might be more than a kilometre below its surface, where an entire network of subglacial lakes has been discovered.

Mars was not always so cold and dry as it is now. There are abundant signs that water flowed across its surface in the distant past, but today you’d struggle to find even any crevices that you could call moist.

There is nevertheless plenty of water on Mars today, but it’s virtually all frozen, so not much use for life. Even in places where the noon-time temperature creeps above freezing, surface signs of liquid water are frustratingly rare. This is because the atmospheric pressure on Mars is too slight to confine water in its liquid state, so ice usually turns directly into vapour when heated.

Lakes beneath ice

It is beginning to look as if the most favourable place for liquid water on Mars is beneath its vast south polar ice cap. On Earth, such lakes began to be discovered in Antarctica in the 1970s, where nearly 400 are now known. Most of these have been found by “radio echo sounding” (essentially radar), in which equipment on a survey aircraft emits radio pulses.

Part of the signal reflects back from the ice surface, but some is reflected from further below – especially strongly where there is a boundary between ice and underlying liquid water. Antarctica’s largest subglacial lake is Lake Vostok – which is 240km long, 50km wide and hundreds of metres deep – located 4km below the surface.

Radar satellite image revealing Lake Vostok below the Antarctic ice. The area shown is about 300km across. NASA

Indications of similar lakes below the southern polar ice cap of Mars were first suggested by radar reflections 1.5km below the ice surface in a region named Ultimi Scopuli. These were detected between May 2012 and December 2015 by MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding), an instrument carried by the European Space Agency’s Mars Express that has been orbiting the planet since 2003.

A 4km wide area in Ultimi Scopuli: strange ice texture gives no clue as to presence of liquid water 1.5km below. NASA/JPL/University of Arizona

The new study of MARSIS data using signal processing techniques that take account of both the intensity and the sharpness (“acuity”) of the reflections has demonstrated that the previously detected region does indeed mark the top of a liquid body. This is the Ultimi Scopuli subglacial lake, and there seem also to be smaller patches of liquid nearby in the 250km by 300km area covered by the survey. The authors suggest that the liquid bodies consist of hypersaline solutions, in which high concentrations of salts are dissolved in water.

They point out that salts of calcium, magnesium, sodium and potassium are known to be ubiquitous in the martian soil, and that dissolved salts could help to explain how subglacial lakes on Mars can remain liquid despite the low temperature at the base of the ice cap. The weight of the overlying ice would supply the pressure necessary to keep the water in liquid state rather than turning to vapour.

Life in subglacial lakes?

Lake Vostok is touted as a possible habitat for life that has been isolated from the Earth’s surface for millions of years, and as an analogue for proposed environments habitable by microbes (and possibly more complex organisms) in the internal oceans of icy moons such as Jupiter’s Europa and Saturn’s Enceladus.

Mars’s south polar ice cap as seen by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, 2000. NASA

Although hypersaline water would give microbes a place to live below Mars’ south polar cap, without an energy (food) source of some kind they could not survive. Chemical reactions between water and rock might release some energy but probably not enough; it would help if there was an occasional volcanic eruption, or at least hot spring, feeding into lake.

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Read more: What on Earth could live in a salt water lake on Mars? An expert explains

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We lack evidence of this on Mars, unlike on Europa and Enceladus. Although the new findings make Mars even more interesting than before, they haven’t advanced its ranking in the list of solar system bodies most likely to host life.

That said, the salty water could act as a preservation chamber – helping us find alien organisms that are now extinct but once came to Mars from other parts of the solar system.

David Rothery, Professor of Planetary Geosciences, The Open University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The four most promising worlds for life in the solar system.

The four most promising worlds for alien life in the solar system

NASA’s Curiosity Rover takes a selfie on Mars in June, 2018. NASA/JPL-Caltech/MSSS, CC BY-SA

Gareth Dorrian, University of Birmingham

The Earth’s biosphere contains all the known ingredients necessary for life as we know it. Broadly speaking these are: liquid water, at least one source of energy, and an inventory of biologically useful elements and molecules.

But the recent discovery of possibly biogenic phosphine in the clouds of Venus reminds us that at least some of these ingredients exist elsewhere in the solar system too. So where are the other most promising locations for extra-terrestrial life?

Mars

Mars is one of the most Earth-like worlds in the solar system. It has a 24.5-hour day, polar ice caps that expand and contract with the seasons, and a large array of surface features that were sculpted by water during the planet’s history.

Mars has polar ice caps. ESA & MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA), CC BY-SA

The detection of a lake beneath the southern polar ice cap and methane in the Martian atmosphere (which varies with the seasons and even the time of day) make Mars a very interesting candidate for life. Methane is significant as it can be produced by biological processes. But the actual source for the methane on Mars is not yet known.

It is possible that life may have gained a foothold, given the evidence that the planet once had a much more benign environment. Today, Mars has a very thin, dry atmosphere comprised almost entirely of carbon dioxide. This offers scant protection from solar and cosmic radiation. If Mars has managed to retain some reserves of water beneath its surface, it is not impossible that life may still exist.

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Read more: Life on Mars? Europe commits to groundbreaking mission to bring back rocks to Earth

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Europa

Europa was discovered by Galileo Galilei in 1610, along with Jupiter’s three other larger moons. It is slightly smaller than Earth’s moon and orbits the gas giant at a distance of some 670,000km once every 3.5 days. Europa is constantly squeezed and stretched by the competing gravitational fields of Jupiter and the other Galilean moons, a process known as tidal flexing.

The moon is believed to be a geologically active world, like the Earth, because the strong tidal flexing heats its rocky, metallic interior and keeps it partially molten.

Europa’s icy surface is a good sign for alien hunters. NASA/JPL-Caltech/SETI Institute, CC BY-SA

The surface of Europa is a vast expanse of water ice. Many scientists think that beneath the frozen surface is a layer of liquid water – a global ocean – which is prevented from freezing by the heat from flexing and which maybe over 100km deep.

Evidence for this ocean includes geysers erupting through cracks in the surface ice, a weak magnetic field and chaotic terrain on the surface, which could have been deformed by ocean currents swirling beneath. This icy shield insulates the subsurface ocean from the extreme cold and vacuum of space, as well as Jupiter’s ferocious radiation belts.

At the bottom of this ocean world it is conceivable that we might find hydrothermal vents and ocean floor volcanoes. On Earth, such features often support very rich and diverse ecosystems.

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Read more: Europa: there may be life on Jupiter's moon and two new missions will pave the way for finding it

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Enceladus

Like Europa, Enceladus is an ice-covered moon with a subsurface ocean of liquid water. Enceladus orbits Saturn and first came to the attention of scientists as a potentially habitable world following the surprise discovery of enormous geysers near the moon’s south pole.

These jets of water escape from large cracks on the surface and, given Enceladus’ weak gravitational field, spray out into space. They are clear evidence of an underground store of liquid water.

Not only was water detected in these geysers but also an array of organic molecules and, crucially, tiny grains of rocky silicate particles that can only be present if the sub-surface ocean water was in physical contact with the rocky ocean floor at a temperature of at least 90˚C. This is very strong evidence for the existence of hydrothermal vents on the ocean floor, providing the chemistry needed for life and localised sources of energy.

Titan

Titan is the largest moon of Saturn and the only moon in the solar system with a substantial atmosphere. It contains a thick orange haze of complex organic molecules and a methane weather system in place of water – complete with seasonal rains, dry periods and surface sand dunes created by wind.

Titan’s atmosphere makes it look like a fuzzy orange ball. NASA/JPL-Caltech/Space Science Institute, CC BY-SA

The atmosphere consists mostly of nitrogen, an important chemical element used in the construction of proteins in all known forms of life. Radar observations have detected the presence of rivers and lakes of liquid methane and ethane and possibly the presence of cryovolcanoes – volcano-like features that erupt liquid water rather than lava. This suggests that Titan, like Europa and Enceladus, has a sub-surface reserve of liquid water.

At such an enormous distance from the Sun, the surface temperatures on Titan are a frigid -180˚C – way too cold for liquid water. However, the bountiful chemicals available on Titan has raised speculation that lifeforms – potentially with fundamentally different chemistry to terrestrial organisms – could exist there.

Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of Birmingham

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Can the Moon be a person?

Can the Moon be a person? As lunar mining looms, a change of perspective could protect Earth's ancient companion

The Apollo 17 lunar lander surrounded by tyre tracks. NASA

Alice Gorman, Flinders University

Everyone is planning to return to the Moon. At least 10 missions by half a dozen nations are scheduled before the end of 2021, and that’s only the beginning.

Even though there are international treaties governing outer space, ambiguity remains about how individuals, nations and corporations can use lunar resources.

In all of this, the Moon is seen as an inert object with no value in its own right.

But should we treat this celestial object, which has been part of the culture of every hominin for millions of years, as just another resource?

The Moon Village Association public forum on August 18 debated whether the Moon should have legal personhood.

Why we should think about legal personhood

In April 2020, US president Donald Trump signed an Executive Order on the use of “off-Earth resources” which made clear his government’s stance towards mining on the Moon and other celestial bodies:

Americans should have the right to engage in commercial exploration, recovery, and use of resources in outer space.

Lunar resources include helium-3 (a possible clean energy source), rare earth elements (used in electronics) and water ice. Located in shadowed craters at the poles, water ice could be used to make fuel for lunar industries and to take the next step on to Mars.

As a thought experiment in how we might regulate lunar exploitation, some have asked whether the Moon should be granted legal personhood, which would give it the right to enter into contracts, own property, and sue other persons.

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Read more: Five ethical questions for how we choose to use the Moon

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Legal personhood is already extended to many non-human entities: certain rivers, deities in some parts of India, and corporations worldwide. Environmental features can’t speak for themselves, so trustees are appointed to act on their behalf, as is the case for the Whanganui River in New Zealand. One proposal is to apply the New Zealand model to the Moon.

Heritage and memory

As a space archaeologist, I study artefacts and places associated with space exploration in the 20th and 21st centuries. Previously, I worked with Indigenous communities to mitigate damage to heritage sites caused by mining. So I have a keen interest in what mining means for human heritage on the Moon.

Places like Tranquility Base, where humans first landed on the Moon in 1969, could be considered heritage for the entire species. There are more than 100 artefacts left at Tranquility Base, including a television camera, experiment packages, and Buzz Aldrin’s space boots.

The Apollo 11 Landing Module, with the Solar Wind Experiment and TV camera in the background. These artefacts were left on the surface on the Moon in 1969. NASA

Objects like this are full of meaning and memory. But these objects not just made by humans – they also shape human behaviour in their own right. It’s in this context that I want to consider two aspects of lunar personhood: memory and agency.

Can we support the legal concept of personhood for the Moon with actual features of personhood?

Does the Moon remember?

The 17th-century philosopher John Locke argued that memory was a key feature of personhood. It’s now acceptable to attribute memory to environmental features on Earth, like the oceans.

There are many different types of memory, of course – think of memory foam, a space-age spin-off with terrestrial applications.

One reason scientists want to study the Moon is to retrieve the memory of how it formed after separating from Earth billions of years ago.

This memory is encoded in geological features like craters and lava fields, and the regions at the lunar poles where shadows two billion years old preserve precious water ice.

Permanently Shadowed Regions at the lunar South Pole in blue, captured by NASA’s Lunar Reconnaissance Orbiter. These unique regions only occur in two other locations in the solar system, Ceres and Mercury. NASA/GFSC

These are like archives storing information about past events. The most recent layer of memory records 60 years of human interventions, sitting lightly on the surface. This belongs to human heritage and memory, but it is now lunar memory too.

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Read more: Friday essay: shadows on the Moon - a tale of ephemeral beauty, humans and hubris

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Does the Moon have agency?

The international Committee on Space Research (COSPAR) maintains the Planetary Protection Policy. This policy aims to prevent harm to potential life on other planets and moons. The Moon requires little protection because it is considered a dead world.

Recently, social media went wild with a story that self-described TikTok witches had hexed the Moon. More experienced WitchTokkers reacted with fury at their hubris in meddling with powers they didn’t understand.

Despite its apparent irrationality, there was something delightful about this story. It showed how the Moon is thought to interact with human life on its own terms. The “witches” took the Moon seriously as an agent in human affairs.

When humans return to the Moon, they will not find it a dead world. It is a very active landscape shaped by dust, shadows and light.

The Moon reacts to human disturbance by mobilising dust that irritates lungs, breaks down seals and prevents equipment from working. This is neither passive nor hostile – just the Moon being itself.

The Moon as an equal partner

Australian philosopher Val Plumwood would see the Moon as a co-participant in human affairs, rather than formless, dead matter:

When the other’s agency is treated as background or denied, we give the other less credit than it is due. We can easily come to take for granted what they provide for us, and to starve them of the resources they need to survive.

So this leaves me with a question: if the Moon is a legal person, what does it need from us to sustain its memory and agency? How can we achieve what Plumwood calls a “mutual flourishing”?

The answers might lie in our attitudes.

We could abandon the idea that our moral obligations only cover living ecologies. We should consider the Moon as an entity beyond the resources it might hold for humans to use.

In practice, this might mean trustees would determine how much of the water ice deposits or other geological features can be used, or set conditions on activities which alter the qualities of the Moon irreversibly.

The record of human activities we leave on the Moon should reflect respect, as we are contributing to what it remembers. In this sense, the TikTok witches had the right idea.

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This article is based on a presentation at a Moon Village Association public forum organised by the Office of Other Spaces, Catapult UK and the Space Junk Podcast, and supported by Inspiring NSW and the Hunter Innovation and Science Hub.

Alice Gorman, Associate Professor in Archaeology and Space Studies, Flinders University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Hydrogen-breathing aliens? Study suggests new approach to finding extraterrestrial life

An exoplanet and its atmosphere pass in front of its star (artist’s impression, from an imaginary point near to the planet). NASA Goddard Space Flight Center

David Rothery, The Open University

The first time we find evidence of life on a planet orbiting another star (an exoplanet), it is probably going to be by analysing the gases in its atmosphere. With the number of known Earth-like planets growing, we could soon discover gases in an exoplanet’s atmosphere that are associated with life on Earth.

But what if alien life uses somewhat different chemistry to ours? A new study, published in Nature Astronomy, argues that our best chances of using atmospheres to find evidence of life is to broaden our search from focusing on planets like our own to include those with a hydrogen atmosphere.

We can probe the atmosphere of an exoplanet when it passes in front of its star. When such a transit happens, the star’s light has to pass through the planet’s atmosphere to reach us and some of it is absorbed as it goes. Looking at the star’s spectrum – its light broken down according to its wavelength – and working out what light is missing because of the transit reveals which gases the atmosphere consists of. Documenting exoplanet atmospheres is one of the goals of the much-delayed James Webb Space Telescope.

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Read more: Exoplanets: how we used chemistry to identify the worlds most likely to host life

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If we were to find an atmosphere that has a different chemical mix to what we would expect, one of the simplest explanations would be that it is maintained that way by living processes. That is the case on Earth. Our planet’s atmosphere contains methane (CH₄), which naturally reacts with oxygen to make carbon dioxide. But the methane is kept topped up by biological processes.

Another way to look at this is that the oxygen wouldn’t be there at all had it not been liberated from carbon dioxide by photosynthetic microbes during the so-called great oxygenation event that began about 2.4 billion years ago.

Look beyond oxygen atmospheres

The authors of the new study argue that we should start investigating worlds larger than the Earth whose atmospheres are dominated by hydrogen. These may not have any free oxygen, because hydrogen and oxygen make a highly flammable mixture.

The hydrogen-filled Hindenberg airship destroyed by fire in 1937. Such a fire could not happen on a world with an oxygen-free hydrogen atmosphere. Murray Becker/Associated Press

Hydrogen is the lightest of all molecules and escapes to space easily. For a rocky planet to have gravity strong enough to hang on to a hydrogen atmosphere, it needs to be a “super-Earth” with a mass between about two and ten times the Earth’s. The hydrogen could either have been captured directly from the gas cloud where the planet grew, or have been released later by a chemical reaction between iron and water.

The density of a hydrogen-dominated atmosphere decreases about 14 times less rapidly the higher up you go than in an atmosphere dominated by nitrogen like the Earth’s. This makes for a 14-times greater envelope of atmosphere surrounding the planet, making it easy to spot in the spectra data. The greater dimensions would also improve our chances of observing such an atmosphere by direct imaging with an optical telescope.

Hydrogen-breathing in the lab

The authors carried out laboratory experiments in which they demonstrated that the bacterium E. coli (billions of which live in your intestines) can survive and multiply under a hydrogen atmosphere in the total absence of any oxygen. They demonstrated the same for a variety of yeast.

Although this is interesting, it does not add much weight to the argument that life could flourish under a hydrogen atmosphere. We already know of many microbes within the Earth’s crust that survive by metabolising hydrogen, and there is even a multicellular organism that spends all its life in an oxygen-free zone on the floor of the Mediterranean.

Spinoloricus, a tiny but multicellular organism that apparently requires no oxygen to live. Scale bar is 50 micrometres. Roberto Danovaro, Antonio Dell'Anno, Antonio Pusceddu, Cristina Gambi, Iben Heiner & Reinhardt Mobjerg Kristensen

Earth’s atmosphere, which started out without oxygen, is unlikely ever to have had more than 1% hydrogen. But early life may have had to metabolise by reacting hydrogen with carbon to form methane, rather than by reacting oxygen with carbon to form carbon dioxide, as humans do.

Biosignature gases

The study did make an important discovery though. The researchers demonstrated that there is an “astonishing diversity” of dozens of gases produced by products in E. coli living under hydrogen. Many of these, such as dimethylsilfide, carbonyl sulfide and isoprene, could be detectable “biosignatures” in a hydrogen atmosphere. This boosts our chances of recognising life signs at an exoplanet – you have to know what to look for.

That said, metabolic processes that use hydrogen are less efficient than those using oxygen. However, hydrogen breathing life is already an established concept so far as astrobiologists are concerned. Sentient hydrogen breathers have even made appearances in some rationally-based science fiction, such as the Uplift novels of David Brin.

The authors of the new study also point out that molecular hydrogen in sufficient concentration can act as a greenhouse gas. This could keep a planet’s surface warm enough for liquid water, and hence surface life, further from its star than would otherwise be the case.

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Read more: Twin civilisations? How life on an exoplanet could spread to its neighbour

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The authors shy away from considering the chances of finding life in giant gas planets like Jupiter. Even so, by expanding the pool of habitable worlds to include super-Earths with hydrogen-rich atmospheres, they have potentially doubled the number of bodies we could probe to find those first elusive signs of extraterrestrial life.

David Rothery, Professor of Planetary Geosciences, The Open University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Space dust fossils are providing a new window onto Earth's past.

Space dust fossils are providing a new window onto Earth’s past

Finding fossil meteorites is a whole new level of difficulty because these rocks are not spread thinly on the surface but, like dinosaur fossils, entombed in ancient rocks. But geologist Professor Birger Schmitz at Lund University in Sweden has discovered a way to find them – and not just the odd rock, but sizeable quantities of fossilised space dust.

It turns out that this can paint a unique picture of how the course of ancient life on Earth was influenced by goings on in space – and has already revealed how space dust from an asteroid collision 466 million years ago could have triggered an ice age. 

Rocks

Meteorites are rocks from space that have fallen on Earth, mostly fragments of the asteroids jostling between Mars and Jupiter.

We know that one huge rock smashed into Earth 66 million years ago, killing off the dinosaurs and most other life. This was first hypothesised by Nobel Prize winner Luis Alvarez and his son Walter, both then based at universities in Berkeley, the US. They led the team that discovered a thin iridium-rich ash layer in sediments globally which formed when the dinosaurs became extinct. Iridium is extremely rare in our planet’s crust and so the team concluded that this element had been delivered by a huge asteroid. The implication was that this cataclysm wiped out the dinosaurs, along with three-quarters of all other living things. 

Prof. Schmitz did his postdoc with the Alvarez team and it’s fair to say it shaped his career. ‘Until their discovery, the evolution of life and the history of Earth was almost always thought of like a closed system,’ said Prof. Schmitz. ‘I became fascinated by trying to connect what goes on in space with what happens on Earth.’

Returning home to Sweden in 1990, Prof. Schmitz read some newspaper reports saying that an amateur geologist named Mario Tassinari had found a few fossil meteorites in the Thorsberg quarry on the southern shore of Lake Vänern. At this time, there were only a handful of fossil meteorites known to science. Was this a chance to study what meteorites had been like millions of years ago and piece together the effects they had on Earth? Prof. Schmitz called Tassinari and they agreed to collaborate on a systematic study of the quarry.

‘(Many of) these meteorites are as different from the meteorites that fall today as some of the animals that were living in that time are compared to today’s animals.’

Prof. Birger Schmitz, Lund University, Sweden

Quarry

The quarry workers carve out sheets of limestone for use as floor tiles. When they find a piece that looks like it might hold a space rock, they call Prof. Schmitz. Each year, they get four or five fossil meteorites. They mostly look like little more than black smudges embedded in the rock, a few centimetres across.

Prof. Schmitz wondered if other quarries might hold similar delights. He also went hunting for meteorites in places with the right kind of floor tiles, such as Paddington station in London.

But it turns out Thorsberg is, as far as we know, a one-off. Special conditions are required to preserve sizeable fossil meteorites in reasonable numbers. You need sediments at the bottom of a body of water that turn to rock very gradually. Slowness is crucial, because that allows more meteorites to accumulate on a small area.

Around 2000, Prof. Schmitz began to think he was finding rather a lot of stones – by this time he had nearly 50 in total. He worked out the amount of rock the quarry workers had carved out each year and divided it by the number of meteorites they found. That told him that back when the rock was formed the flux of meteorites, the number falling on a given area in a given time, was about 100 times greater than it is today. An area the size of Wales would have been getting not two meteorites a year, but 200.

‘I still remember the day I thought of this,’ said Prof. Schmitz. ‘I went immediately to the quarry. “Can I see your logbooks? Are you sure you’ve found such a large number of meteorites in such a small area?”’

There was no mistake. And Prof. Schmitz quickly came up with an explanation. ‘There is one very likely scenario: that if something explodes in space and breaks up into billions and billions of small pieces – well, what we saw in the quarry, that's exactly what would happen.’

In 2004, Prof. Schmitz and researchers at ETH-Zürich, Switzerland, published a paper detailing analyses of the fossil meteorites found. This showed that the meteorites had been in space for relatively short stretches of time – about a million years – by looking at the effect of cosmic rays on their mineralogy. He concluded that a violent collision had exploded them onto an Earth-bound trajectory. Still, these stones were small fry in the grand scheme of things; nowhere near large enough to cause an impact that would significantly affect Earth’s history.

You might think that Prof. Schmitz would have wanted to find something bigger. But it doesn’t work like that. It turns out that hefty meteorites are rare, but smaller ones are more common.

Space dust

Micrometeorites, otherwise known as space dust, are the most common of all: it’s estimated that today we get showered with 100 tonnes of this stuff each day. Prof. Schmitz reasoned that it must be strewn throughout the limestone in Thorsberg quarry too – if only there was a way to find it.

One mineral, chromite, in micrometeorites is incredibly hardy: ‘It’s extremely resistant, it survives everything,’ said Prof. Schmitz.

That gave him an idea, which he investigated through a project called Astrogeobiosphere. ‘I told my poor student the time, “Niklas, take 5 kilograms of rock and dissolve it in hydrochloric acid.”’

Doing so resulted in 10 tiny fragments of extraterrestrial chromite, each a tenth of a millimetre long. And repeating this at intervals in the limestone revealed there was a huge uptick in space dust in 466 million year old rock, results that Prof. Schmitz published in 2019.

The space dust arrival coincides with a cold period known as the mid-Ordovician ice age. Prof. Schmitz concluded that a massive collision in the asteroid belt spewed out both large meteorites and a gargantuan cloud of dust, which blocked lots of sunlight from reaching Earth, leading to an ice age. After the asteroid that killed the dinosaurs, it would be the second example of an event in the wider cosmos profoundly influencing Earth’s story.

‘I think this is a hugely exciting story,’ said Dr Katie Joy, a planetary scientist at the University of Manchester, UK. ‘It’s a massive amount of work and I don’t envy them, having to crush up tonnes and tonnes and rock and passing it through acid.’

She adds that there is still work to be done to understand the biases in the sample. The minerals Prof. Schmitz is studying are not found in every sort of asteroid and comet, which means they do not represent all the rock types that have fallen from space to Earth. ‘This record is a partial record,’ she said.

Through Astrogeobiosphere, Prof. Schmitz has taken this work even further by dissolving 20 tonnes of rock from different quarries, with samples from each representing different periods in Earth’s deep history. The idea was to provide the first sketch of how incoming space dust has varied over time.

He says this work is done and he and his team have a collection of different meteorites that fell on Earth in the distant past – but it won’t be published for a few months. However, fossil meteorites continue to reveal new information about Earth's past.

‘(Many of) these meteorites are as different from the meteorites that fall today as some of the animals that were living in that time are compared to today’s animals,’ he said.

The research in this article was funded by the European Research Council. If you liked this article, please consider sharing it on social media.

This post Space dust fossils are providing a new window onto Earth’s past was originally published on Horizon: the EU Research & Innovation magazine | European Commission.

How astronomers are piecing together the mysterious origins of superluminous supernovae

Known as superluminous supernovae, these events are typically 10 to 100 times brighter than a regular supernova but much more rare. We’ve spotted about 100 so far, but many aspects of these events remain elusive.

Why are they so much brighter than regular supernovae, for example, and what stars cause them? Astronomers are hoping to answer these and more questions in the coming years, with various studies underway to understand these events like never before.

Formation

Dr Ragnhild Lunnan from Stockholm University, Sweden, is one of the co-investigators on the SUPERS project, which is attempting to work out what stars lead to the formation of superluminous supernovae. With dozens found already, the team are building the largest collection of these events in an effort to learn more about them.

‘By following the evolution of these supernovae into a very late phase, you can decode their (structure),’ she said. ‘This tells you things about the star that exploded, and possibly how it exploded.’

To find these explosions, Dr Lunnan and her team are making use of a camera called the Zwicky Transient Facility (ZTF), part of the Palomar Observatory in California, US, to survey the sky. Only one supernova is expected per galaxy per century, with only one in 1,000 or even one in 10,000 of those being superluminous. But by looking at many galaxies simultaneously with the ZTF, it’s possible to spot these events.

Superluminous supernovae are found more often in star-forming galaxies than older galaxies, which means they are likely explosions of young stars, notes Dr Lunnan.

‘Additionally, you very often find them in galaxies that are kind of chemically primitive, called low-metallicity, and we think this is also a clue,’ she said. ‘We think they’re associated with very massive and metal-poor stars. But beyond that, we really don’t know.’

In 2018, Dr Lunnan and her team discovered a superluminous supernova with a giant shell of material around it, which it must have ejected in the final years of its short life. ‘That discovery (of the shell) is another clue that the stars must be very massive,’ said Dr Lunnan.

‘You very often find them in galaxies that are kind of chemically primitive, called low-metallicity, and we think this is also a clue.’

Dr Ragnhild Lunnan, Stockholm University, Sweden

Going supernova

The exact process that causes a superluminous supernova is another question. Typically, stars can go supernova either by independently collapsing, or sharing material with a small dense star known as a white dwarf before an explosion takes place, known as a Type 1a supernova. But what happens in a superluminous event?

Dr Avishay Gal-Yam from the Weizmann Institute of Science in Israel, project coordinator on the Fireworks project, has been trying to answer this question. The project has been using observations of the night sky from cameras like the ZTF that have a rapid cadence, meaning they show an event shortly after it occurred, to study cosmic explosions.

Previously we would only see supernovae about two weeks after they happened, but ZTF’s constant observations of the sky allows us to see them within about one or two days. And that’s particularly useful for superluminous supernovae. A regular supernova can brighten and fade over a period of weeks, but a superluminous supernovae can last several times longer, while also reaching its peak brightness slower.

‘They are relatively slowly evolving,’ he said. ‘The time for the explosion to reach its peak could be a couple of months, sometimes even longer. So studies of these objects are not focused on rapid observations, but rather a continuous follow-up campaign which takes months and sometimes years.’

So far Dr Gal-Yam and his team have published several studies, examining some of the theories for how these events happen. One idea is that a regular supernova leaves behind a rapidly spinning and highly magnetised neutron star, called a magnetar, which acts as a giant magnet and pumps energy into the supernova explosion.

But Dr Gal-Yam’s more favoured theory is the same advocated by Dr Lunnan – that collapsing massive stars are the cause. ‘What can generate so much energy that can power such a luminous emissions, both in terms of the amount of energy and the very long amount of time the emission continues to happen?’ he said. ‘The most intriguing (theory) is an explosion from a very massive star 100 times more massive than the sun.’

Distance

While many questions about superluminous supernovae remain unanswered, they are already proving useful as distance markers in the universe. Called ‘standard candles’, bright events like supernovae can tell us how far away a particular galaxy is as we know how bright they should be.

‘The idea here is a standard candle, an object of known luminosity,’ said Dr Mark Sullivan, project coordinator on the SPCND project that looked at how explosive events like this might be useful for cosmological studies. ‘If you can find it in the sky and measure how bright it appears to be to us on Earth, you can tell how far away it is.’

The brightness of superluminous supernovae makes them particularly useful. Using the Dark Energy Survey (DES), a survey of the night sky using the Cerro Tololo Inter-American Observatory in Chile, Dr Sullivan and his team found more than 20 superluminous supernovae in galaxies up to eight billion light-years from Earth, giving us a new cosmic distance ladder. ‘We got a new data set of these objects in the distant universe,’ said Sullivan.

With a growing sample size of these events, astronomers will now be hoping to answer once and for all what causes them. Upcoming telescopes like the Vera C. Rubin Observatory in Chile could prove vital, performing new sweeping surveys of the night sky, and finding more of these objects than ever before.

‘We really are in this era where we’re finding so many objects – even things that are rare,’ said Dr Lunnan. ‘It’s a lot of fun.’

The research in this article was funded by the EU. If you liked this article, please consider sharing it on social media.

This post How astronomers are piecing together the mysterious origins of superluminous supernovae was originally published on Horizon: the EU Research & Innovation magazine | European Commission.

Earth's magnetic field may change faster than we thought.

 

Earth’s magnetic field may change faster than we thought – new research

It’s long been a mystery how fast the Earth’s magnetic field changes. Andrey VP/Shutterstock

Christopher Davies, University of Leeds

The Earth’s magnetic field, generated 3,000km below our feet in the liquid iron core, is crucially important to life on our planet. It extends out into space, wrapping us in an electromagnetic blanket that shields the atmosphere and satellites from solar radiation.

Yet the magnetic field is constantly changing in both its strength and direction and has undergone some dramatic shifts in the past. This includes enigmatic reversals of the magnetic poles, with the south pole becoming the north pole and vice versa.

A long-standing question has been how fast the field can change. Our new study, published in Nature Communications, has uncovered some answers.

Rapid changes of the magnetic field are of great interest because they represent the most extreme behaviour of the ocean of molten iron in the liquid core. By tying the observed changes to core processes, we can learn important information about an otherwise inaccessible region of our planet.

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Read more: Why the Earth's magnetic poles could be about to swap places – and how it would affect us

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Historically, the fastest changes in Earth’s magnetic field have been associated with reversals, which occur at irregular intervals a few times every million years. But we discovered field changes that are much faster and more recent than any of the data associated with actual reversals.

Magnetic reversal. NASA.

Nowadays satellites help monitor changes in the field in both space and time, complemented by navigational records and ground-based observatories. This information reveals that changes in the modern field are rather ponderous, around a tenth of a degree per year. But, while we know that the field has existed for at least 3.5 billion years, we don’t know much about its behaviour prior to 400 years ago.

To track the ancient field, scientists analyse the magnetism recorded by sediments, lava flows and human-made artefacts. That’s because these materials contain microscopic magnetic grains that record the signature of Earth’s field at the time they cooled (for lavas) or were added to the landmass (for sediments). Sediment records from central Italy around the time of the last polarity reversal almost 800,000 years ago suggest relatively rapid field changes reaching one degree per year.

Such measurements, however, are extremely challenging, with results still being debated. For example, there are uncertainties in the process by which sediments acquire their magnetism.

Improved measurements

Our research takes a different approach by using computer models based on the physics of the field generation process. This is combined with a recently published reconstruction of global variations in Earth’s magnetic field spanning the last 100,000 years, based on a compilation of measurements from sediments, lavas and artefacts.

This shows that changes in the direction of Earth’s magnetic field reached rates that are up to ten degrees per year – ten times larger than the fastest currently reported variations.

The fastest observed changes in the geomagnetic field direction occurred around 39,000 years ago. This shift was associated with a locally weak field in a confined region just off the west coast of central America. The event followed the global “Laschamp excursion” – a “failed reversal” of the Earth’s magnetic field around 41,000 years ago in which the magnetic poles briefly moved far from the geographic poles before returning.

The fastest changes appear to be associated with local weakening of the magnetic field. Our model suggests this is caused by movement of patches of intense magnetic field across the surface of the liquid core. These patches are more prevalent at lower latitudes, suggesting that future searches for rapid changes in direction should focus on these areas.

The impact on society

Changes in the magnetic field, such as reversals, probably don’t pose a threat to life. Humans did manage to live through the dramatic Laschamp excursion. Today, the threat is mainly down to our reliance on electronic infrastructure. Space weather events such as geomagnetic storms, arising from the interaction between the magnetic field and incoming solar radiation, could disrupt satellite communications, GPS and power grids.

Satellites are at risk from space weather. Andrey Armyagov/Shutterstock

This is troubling – the economic cost of a collapse of the US power grid due to a space-weather event has been estimated at around one trillion dollars. The threat is serious enough for space weather to appear as a high priority on the UK national risk register.

Space weather events tend to be more prevalent in regions where the magnetic field is weak – something we know can happen when the field is changing rapidly. Unfortunately, computer simulations suggest that directional changes arise after the field strength begins to weaken, meaning we cannot predict dips in field strength by just monitoring the field direction. Future work using more advanced simulations can shed more light on this issue.

Is another rapid change in the magnetic field on its way? This is very hard to answer. The fastest changes are also the rarest events: for example, the changes identified around the Laschamp excursion are over two times faster than any other changes occurring over the last 100,000 years.

This makes it difficult for scientists to predict rapid changes – they are “black swan events” that come as a surprise and have a big impact. One possible route forward is to use physics-based models of how the field behaves as part of the forecast.

We still have a lot to learn about the “speed limit” of Earth’s magnetic field. Rapid changes have not yet been directly observed during a polarity reversal, but they should be expected since the field is thought to become globally weak at these times.

Christopher Davies, Associate professor, University of Leeds

This article is republished from The Conversation under a Creative Commons license. Read the original article.

METEOR SHOWERS 2020

Let's take a brief look at some of the upcoming meteor showers for 2020.

So far we have seen the Quadrantids on January 4 2020.

Let’s take a look at some of the remaining meteor showers for 2020. Please note these are from a Southern Hemisphere perspective, please check your favourite App or planetarium software to see where and when these showers will be best visible to you in the more northern latitudes.
All the images below are taken from SkySafari 6Pro, a link to the webpage is in the right column on this page.

THE LYRIDS METEOR SHOWER, APRIL 22 2020.

The Lyrids appear in late April of each year and are associated with comet Thatcher from 1861.

The Lyrids can be seen anywhere between the 15^th and 25th of April, this year they will peak on the 22^nd of April.

The radiant for this shower is in the constellation Lyra and is best seen from the Northern Hemisphere. From the Southern hemisphere you might get lucky and see a few low on your Northern horizon, the constellation Lyra will be about 20 degrees above the horizon just after 4AM(From South Africa), so a early morning view.

Check your favourite planetarium app or software to determine when it will be best viewed from your location.

This shower can produce between 10 to 15 meteors per hour but could also have a surge of up 100 PH, although not very common but they do make the Lyrids more unpredictable and interesting.

THE ETA AQUARIIDS MAY 5 2020.

The Eta Aquariids are seen in early May each year and are best seen at 4AM on the morning of the 5^th May.

The quadrant for this meteor shower lies in the constellation Aquarius and is associated with the periodic comet 1P/Halley.

This meteor shower is best suited to those of us in the Southern Hemisphere with a hourly average of a meteor per minute. From the more northerly latitudes expect to see far less numbers.

On the morning of the 5^th look to your eastern horizon and the constellation Aquarius as they meteors appear to radiate from it.

Once again it is best suited to early morning viewing as Aquarius rises in the east at around 2AM with the sun rising at 6AM, so probably best from about 3 to 5 AM.

Also of interest here are the planets in the same area of sky, be sure to look for Jupiter, Saturn, Mars naked eye and in the scope you can also see Pluto and Neptune, so might be worth getting the scope out too.

THE DELTA AQUARIIDS, LATE JULY.

Once again the Delta Aquariids are best suited to us here in the Southern hemisphere. These do not have a peak but are probably best seen between the 27^th and 30^th of July and it is thought they may originate from comet 96P/Machholz

Expect to see a average of 15-20 per hour under darker skies as many of these are very feint meteors, so less under more polluted skies.

Again the meteors quadrant lies in the constellation Aquarius.

Look this time to your Western horizon a hour or two before dawn to catch sight of the show in the constellation Aquarius.

THE PERSEIDS, 9-14 AUGUST 2020.

I include this meteor shower since it is by far the most popular even though it is a bust here in the Southern Hemisphere.

Expect to see anything from 50-100 meteors per our that originate from periodic comet Swift-Tuttle.

This meteor shower has it’s quadrant in the constellation Perseus.

From the Southern Hemisphere you will need to look to your Northern horizon and the constellation Perseus, again this is best seen in the early hours before sunrise.

THE NORTHERN AND SOUTHERN TAURIDS.

The Southern Taurids start from 25 September through 25^th November and the Northern Taurids run from October 12^th to December 5^th.

Although these last for quite some time they only produce a sprinkling of meteors with averages around 5 per hour, however they do produce nice fireballs!

To see the Northern Taurids look toward your NW horizon and the constellation Taurus from October 12^th to December 2^nd.

To see the Southern Taurids look toward your Western horizon and the constellation Taurus from 25^th September to 25^th November.

THE LEONIDS, NOVEMBER 17 2020.

This is one of the better meteor showers that produces everything from fireballs and Earthgrazers to meteor storms!

This shower is associated with comet Temple-Tuttle.

Every 33 years Earth passes through the densest dust and that is when the spectacular meteor storms are produced, the last such storm occurred in 2002. During the 1966 storm over 1000 meteors per hour fell into the Earths atmosphere in a 15 minute period!

Again this shower is best seen in the early morning hours before sunrise, look toward your N, NE horizon for the constellation Leo as this is where the quadrant for this shower lies.

These will probably be the best meteor showers for you to see, in my opinion, from our southerly latitudes for this year, there are others but they do not offer as much as the above.

So have fun and get out there and make a wish on a falling star!