Sunday 27 September 2020

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.

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.

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.

Jupiter's white with brown streaks moon Europa in space, — 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.

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.

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.

Sunday 13 September 2020

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.

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.

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.

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