Since free will is so unreliable; cultures, religions, and empires start creating these codes of conduct that dictate the approved method for nearly every aspect of people’s lives. But fast forward a few millennia and suddenly people started to live lives disconnected from the land and subsistence.
Our future in space relies on settling the Moon and using it as a base to probe the deepest questions in the cosmos
is Homewood Research Professor of Physics and Astronomy at Johns Hopkins University in Baltimore. He was awarded the 2011 Balzan Prize for his pioneering work on the infant Universe. His most recent book is Back to the Moon: The Next Giant Leap for Humankind (2022).
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From Blue Origin and SpaceX, to the new James Webb Space Telescope, to space agencies worldwide, we’ve set our sights on distant worlds. The search is on for an Earth-like exoplanet in a solar system light-years away. Closer to home, we’ll soon be excavating the icy moons of Jupiter for life in watery realms. There’s a global drive to develop the Red Planet, Mars, where proposals include human outposts, tourism, and an intensive search for ancient life. Mars may loom in our collective imaginations as the next world out, but prospects for humans living there are actually dim. The landscape is arid, and Martian dust is especially toxic. The trip to Mars would expose travellers to lethal levels of radiation, which engineers and astrobiologists are hoping to mitigate eventually. Since the long voyage to Mars is currently too dangerous for crewed travel, robotic exploration there will likely dominate for several decades to come.
But one celestial body is now within reach for human exploration and exploitation: the Moon. When you get right down to it, despite our dreams of travelling far, the orbiting body next door, the Moon, is our next real target – and the true portal to the cosmos at large.
Humans haven’t set foot on the Moon since Apollo 17 brought Eugene Cernan to the surface on 12 December 1972. Now it’s time to return. Reaching the Moon again is practical. It is an essential first step to exploration of the distant Universe. And it is inevitable. Only from the lunar surface can we mount the ultimate search for our origins. We’ll achieve this by constructing novel telescopes of unprecedented scope in dark lunar craters and on the far side of the Moon.
A s it happens, driven by a desire for extraterrestrial tourism and a new frontier for resources, we are returning to the Moon in force. Several countries are involved, largely motivated by commercial prospects. The resulting lunar infrastructure will open the way to building powerful telescopes that will provide new vistas into key questions that have long obsessed humanity. Where did we come from? And are we alone in this vast Universe?
Space exploration is our destiny, but we can only fulfil it, only discover the deepest mysteries of our Universe, by first returning to the Moon. Many commercial activities are already on the drawing board, spearheaded by space agencies and the private sector alike. Mining rare earth elements. Rocket fuel production. Low-gravity manufacturing. And tourism.
The Moon offers dazzling new horizons for leisure and sports activities. Transport for the first decades of human lunar travel will be expensive. But there is a pent-up demand for luxury tourism. Today’s overwhelming demand will be addressed initially with orbital trips around the Moon. Tickets are already being sold by the likes of SpaceX for launches planned within five years. Tourist lunar landings may now seem pure fantasy, but the will is there.
Such a hugely commercial activity, with vast potential returns, is attracting some of the wealthiest entrepreneurs on our planet. Imagine resort complexes. Lunar golf, with mile-long drives. Buggy rides on the lunar soil, or regolith. Vistas of Earth rising at lunar dawn.
Lunar mining may provide an effectively limitless supply of rare earth elements
The Moon will initially be a playground for the super-rich. Their appetite for new forms of tourism seems insatiable. However, access is certain to change over time once low-cost space transport systems are developed. We would establish giant lunar parks for leisure and relaxation. Low-cost housing would be designed to host the necessary support personnel. Mass tourism will have its day. Commercial backing will certainly fund these activities.
That’s just the beginning. As reserves of rare earth elements are depleted on Earth, lunar resources will step up to the task. Lunar mining may provide an effectively limitless supply of them. Rare earth elements are central to present and future technologies. Mining companies will race to address the challenge of lunar extraction. The potential rewards are enormous.
Here on Earth, scientists project that we will exhaust rare earth elements in less than 1,000 years. Yet bombardment of the Moon by asteroids over billions of years has deposited trillions of tons of rare earths on the lunar surface, based on analysis of the Apollo lunar samples. This amounts to 10,000 times the terrestrial reserves.
Rare earth elements are mined on Earth through environmentally polluting operations. This is such a toxic process that extraction is highly restricted. We can limit the inevitable pollution with robotically aided extraction, and lunar launch sites will facilitate ejection of toxic debris into space. Rare earth elements are key to present and future technologies. It will be difficult for mining companies to resist the challenges of lunar extraction. The potential rewards are enormous.
Because they are ideal for production of rocket fuel, lunar and cislunar (between Earth and Moon) environments will serve as launch sites for interplanetary space probes. The needed fuel, in the form of liquid hydrogen and oxygen, would be sourced from ice deposits in cold polar craters. Rocket fuel depots and spaceports are the future. Lunar fuel resources are a key component of interplanetary travel. We will make use of low lunar gravity to launch spacecraft throughout the solar system. Lunar spaceports will eventually serve as gateways to the stars.
P erhaps the most important outcome from our return to the Moon will be an explosion of pure science. We can build huge telescopes on the Moon to peer further back in time than we could ever do from Earth, or even in space. We must look beyond the compelling goals of lunar and even interplanetary exploration along with commercially driven projects to seek answers to the most fundamental questions ever posed by humanity: where did we come from? Are we alone in this vast Universe? Telescopes will eventually provide the answers, but on a scale beyond our current dreams.
Giant telescopes can be constructed in dark lunar craters near the lunar poles, where the Sun never rises. There’s no atmosphere to limit our view. Stars don’t twinkle, they shine as brilliant points of light. Such clarity is crucial if we are to search for distant planetary systems. There are sites with unlimited solar power on the tall crater rims to power our instruments. Here the Sun never sets. Yet there is extreme cold in the deep crater basins that remain in permanent shadow.
From the Moon, we can search throughout the infrared spectrum for the elusive molecular signatures of life. These might involve oxygen and carbon dioxide in planetary atmospheres, and more complex molecular tracers. Photosynthesis generates a characteristic signature, microbes produce phosphine, cows belch methane. Human activity generates pollutants. Nuclear explosions generate radioactivity.
We need to search huge numbers of exoplanets for the elusive signatures of life
Such signatures may be very rare. The conditions for the origin of life are unknown. Based on what we know of the solar system, life is a rare phenomenon. We have no idea how complex organisms might evolve. There are many random evolutionary directions that lead nowhere. Darwinian evolution is often invoked. It seems to have worked on Earth but, for all we know, it could have been an immensely improbable fluke. We might even be alone in the Universe.
The ultimate challenge is seeking signs of intelligent life. Distant civilisations could exist. There are billions of exoplanets in our galaxy. Even if life was incredibly rare, there might well be candidates. Most of these are billions of years older than Earth. Such exoplanets, if inhabited, would inevitably be thousands or even millions of years ahead of us in evolution. And in technology. They would have had so much more time to evolve.
The comforting thought is that any such advanced civilisations could accomplish interstellar travel. However, intelligent life is likely to be rare and relatively short-lived; this we know because we haven’t yet encountered any advanced civilisations and because of the potential existential catastrophes that await us. These span global epidemics to nuclear wars and major asteroid impacts. Since the number of likely targets with signs of life is small, we need to search huge numbers of exoplanets for the elusive signatures of life.
To seek out signatures of life in nearby exoplanets, future space telescopes will focus on spectral features in their atmospheres. But we will need more than spectral coverage if we are to seek robust indicators of life in the Universe.
Above all, we need many targets. Exoplanets with rocky cores and Earth-like masses are preferred. Such relatively low-mass exoplanets are hard to detect. It’s the larger ones we find most easily. And these are gas giants like Jupiters or Neptunes, hardly congenial to life. Exoplanets need to have rocky cores and be in habitable zones around Sun-like stars for conditions required for life as we know it. After all, that’s the only known criterion for life. No guarantees, but we have just the one example, our Earth.
W e have detected only a handful of exoplanet Earth twins so far. Unfortunately, we have little idea of how terrestrial life originated. So we need to greatly boost the statistics. Numbers count. And we will need light-gathering power to examine the atmospheric spectrum of our targets.
Is there oxygen? Carbon dioxide? Methane? The list of biological tracers goes on. This means digging deeply into the infrared region of the electromagnetic spectrum. And that requires a really large telescope if we are to see far away.
We can’t do this from Earth, where the available spectrum is highly constrained by our atmosphere. The world’s largest telescope, now in construction in the high Atacama Desert in Chile, has a diameter of 39 metres. But even this won’t get us far into the infrared region where our prime signatures of extraterrestrial biology are to be found.
Space telescopes are one option. However, current plans for space telescopes in the next decades envisage apertures of just tens of metres. It’s simply too expensive to launch larger free-flyers.
We need to build much larger telescopes still.
The Moon offers the only solution. We will be there. Transporters and infrastructure will be in place. Incremental costs to such a megaproject should be tolerable. We will build telescopes hundreds of metres in aperture in permanently dark lunar craters. With no winds and low gravity, there is no technological limit. And there are futuristic ideas on how to build crater-spanning telescopes that are kilometres in diameter.
Huge lunar telescopes will explore the first galaxies and stars in unprecedented detail
With these, we could image the nearest exoplanets, such as those around Alpha Centauri, our nearest stellar neighbour some four light-years away. We could detect oceans. We could detect the night glow of any large cities.
The deeper we can search, the more likely we are to sample varied life-friendly environments. We don’t know what to expect, and we are certain that life is fragile and that life tracers are rare. We need many targets. And this requires monstrous megatelescopes, with enormous light-collecting apertures.
Only by detecting unprecedented numbers of Earth-like planets can we hope to optimise our chances of finding signs of extraterrestrial life. We may finally answer one of humanity’s ultimate questions: are we alone?
Huge lunar telescopes will also explore the first galaxies and stars in the Universe in unprecedented detail. They will investigate the first massive black holes that we see shining as quasars. Such black holes are monstrous objects, weighing millions or even billions of solar masses. They are found in the centres of galaxies. Even our Milky Way galaxy hosts such a monster in its centre.
Which formed first, the galaxy or the black hole itself? Amazingly, we don’t know. We see massive galaxies and black holes appear in the distant Universe, as far back as we can see. A huge black hole can form directly from collapse of a massive cloud of gas. Perhaps the black holes seeded the galaxies as their violent activity triggered star formation. Or did the massive black holes grow only by gathering vast amounts of densely packed stars in the hearts of galaxies?
We don’t know. With large lunar telescopes, we can learn about the dawn of the Universe. We will see the end of the dark ages, before there were stars and the first starlight that heralded a new cosmic age.
T he most intimate secrets of the dark ages are best probed with a very different type of telescope, a radio telescope capable of detecting the hydrogen clouds that were the raw material of galaxies. Specifically, we will need a special type of radio telescope operating at very low radio frequencies. And the far side of the Moon is a unique site for a low-frequency radio observatory.
At low radio frequencies, we can look far into the early Universe, answering the fundamental question: where did we come from? Indeed, nearby clouds of hydrogen gas are observed at the easy-to-detect-frequency of 1,420 megahertz (MHz).
As the clouds become more distant, their frequencies decrease dramatically. That is because the expansion of the Universe stretches the wavelength of the light received from distant galaxies toward the red end of the visible spectrum. (Hence we say the light is redshifted.) Those longer, redshifted waves with their lower frequency are too ‘dim’ for the telescopes of today. At such low radio frequencies, the terrestrial ionosphere simply scatters low-frequency radio waves from deep space. Terrestrial radio noise created by marine radars, radio and TV broadcasting, and cellphones all get in the way.
But we won’t have this problem on the far side of the Moon, the most radio-quiet spot in the inner solar system, and the perfect place for low-frequency radio astronomy.
We must go to the lowest radio frequencies. Remember, the Universe is expanding and the energy of photons decreases with time. So detecting hydrogen at low frequency takes us back in time. The expansion of space lowers the frequency of these radio waves to the limits of what is observable. By searching for hydrogen clouds at a frequency of, say, 30 MHz, we peer back to a time long before there were any galaxies. Using telescopes on the Moon, we’ll map their radio shadows and finally start to answer the fundamental question: where did we come from?
The dark ages are our only hope. They are completely unexplored territory
Our astronomers have already explored the fossil radiation from the Big Bang and the cosmic microwave background that has existed from the beginning of time. Sure, we have uncovered the seeds of creation, the fluctuations that seeded galaxies. Yet the data is limited. Ultimately, the signals we tap come from a few million independent points in the sky. We are striving to do better. But we risk running out of information in the microwave sky.
Much more accuracy will be needed to test the greatest question of all – the cosmic origin hypothesis. Did we begin in a Big Bang, causing the Universe to inflate? To test this, we will need to look more deeply and sensitively into the past. This is where exploration of the dark ages can be a game changer – provided that we can extract more information from the sky than current approaches allow.
Already there are planned surveys of galaxies to be conducted by the Nancy Grace Roman Space Telescope and others over the next decade. But we are limited by the number of detectable galaxies.
There is only one way to beef up the precision of cosmology: get more information. With millions of clouds required to form a typical galaxy, the dark ages are our only hope. They are completely unexplored territory. They certainly present an enormous challenge, but they also offer a unique glimpse of the beginning.
T he ultimate precision will come when we optimise the information content of our signal. Typical future surveys will target billions of galaxies. But there are so many more remote clouds of hydrogen, the building blocks of massive galaxies. Probing the dark ages will open up a trillion bits of information and allow a huge increase in precision over surveys of all the galaxies in the visible Universe. By moving to the dark ages and focusing on low-frequency radio signals, we can take a giant step forward.
As current theory holds, inflation of the early Universe occurred in the first 10 -36 second. Then the Universe was teeming with particles and antiparticles that come and go over immeasurably small times. This creates a sort of effervescent quantum foam in what otherwise is a vacuum. In other words, the vacuum has energy. It is this energy that drives inflation. This phase does not last long; the quantum fluctuations are over as soon as space continues to expand and the matter cools slightly, though a trace is left behind in infinitesimal seeds of future structure. The end of inflation is where the cosmic journey begins.
It’s a compelling story. Yet we have little direct evidence of the beginning. To make progress, we need to probe the final unexplored frontier of the early Universe, the dark ages. This epoch provides our clearest glimpse of the Universe before any stars formed. The gaseous building blocks of galaxies were all that existed in terms of structure. These are seen as fossil shadows against the primordial radio glow from the Big Bang. They are ghosts from the past. And with better telescopes capable of detecting very low radio frequencies, these ghosts can help us probe the end of inflation. This is achievable via telescopes on the lunar far side.
Here is the link that will help us attack the ultimate mystery of inflation. The fluctuations in the hydrogen absorption signal are not totally random. They have some slight asymmetry in their distribution of strengths. The asymmetry amounts to a primordial deviation from the usual bell-shaped curve that describes any random distribution. Inflation predicts tiny deviations from randomness in the primordial density fluctuations. This effect has yet to be measured. But it is a robust prediction, true for all inflation models.
Piggybacking on lunar infrastructure meant for industry and tourism opens up new options for science
In short, we seek a very small radio-wave effect in those ancient clouds. We’ll need a huge increase in our current experimental sensitivity to detect it. Remember, elemental hydrogen is comprised of a single electron orbiting a single proton. The radio waves in question are generated when electrons orbiting their protons flip their spin due to a collision with neighbouring atoms. When in the original position – when electron and proton are aligned – hydrogen has a lower energy signal. When the electron has been knocked out of alignment by the impinging light of the Universe, its spin-flips and the radio frequency is higher. By seeking out the lower frequency of the original cloud, we can detect the shadow of a remote cloud of hydrogen, against the cosmic background radiation. In short, studying the extremely faint shadows imprinted on the radio sky from early times can be done only at very low radio frequencies. A telescope on the far side of the Moon is by far our best bet for achieving that goal.
The discovery potential is vast, from the radio to the infrared and optical domains, and even beyond. As yet, little attention has been given to the unique advantages of a lunar platform for studying the Universe. A standalone giant telescope project is inconceivable for budgetary reasons. Instead, to cover the cost, lunar telescopes should be a key component of future lunar settlements. Piggybacking on lunar infrastructure meant for industry and tourism opens up new options for science. Telescopes built alongside other megaprojects will be a minor overhead, all in all.
Rewards include advances in planetary science and a deep understanding of the origin of the Moon. Astronomers will be able to image distant exoplanets and the first stars. The most extraordinary new frontier will be probing the dark ages of the Universe, just as a geologist studies the origins of progressively older layers of rocks here on Earth. In space, our rocks and fossils are the hydrogen clouds from which the galaxies formed.
In order to achieve this vision, it must be integral to lunar projects from the earliest stages of planning. There is an irrefutable case to be made for science-driven projects integrated into commercial activities. The scale for all these ventures is decades or more, but the time to embrace the intent is now.
What can we achieve with such megatelescopes? We will find out if there are remote planets conducive to life. We will look back to our origins. We will see the primeval dawn of the stars. We will seek out the first monster black holes in the Universe.
We hope to answer humanity’s most fundamental questions: where did we come from? Are we alone? There is a compelling scientific case to be made now for a new era of unparalleled exploration to visualise the edge of the Universe from the surface of the Moon.
The forest through the trees.
We can all recall those moments when the pressures of life close in around us and we strive desperately to allay our doubts long enough to survive the ordeal in front of us. A completely natural phenomenon, our brains delivering chemicals to our bodies to enhance reaction speed and decision-making. Hormones drawing us closer to each other and reinforcing our need for family and community.
However, not everything that is natural serves us or is even good for us in the long run. And too often we exit these times of crisis so grateful to have survived and so exhausted from the effort that we don’t take time to evaluate how we performed under that pressure.
Here is where life design thrives. Choosing a design approach allows you to step out of your own shoes for a moment. Take a deep breath. Look at your life, your relationships and ultimately your outcomes. Design asks “Are these relationships, lifestyles, and outcomes preferred?” “How does it feel while getting there?” This creates a very powerful ability to say yes and no to individual components while focusing on preferred outcomes instead of ideology. In simple terms, we get to evaluate the forest instead of tripping on the trees.
Getting to what matters
The driving question here is: do you know what you really want? Are you crystal clear about what outcomes you desire from the different aspects of your life? A life design approach demands we become curious about how we prefer life to function. The advantage here is twofold:
- A design approach allows us to evaluate our lives piece by piece without requiring value judgments. We are not compelled to be weighted by a history of pride or self-prejudice, but rather a simple, piercing question of preferred function. Am I as healthy as I would prefer? Are my relationships as fulfilling as I would prefer? Is my art as challenging or compelling as I would prefer?
- Life design creates a safe space to question function under diverse scenarios. The same philosophy that drives stress tests, wind tunnels and waterproofing is the same idea you can use to address how our life looks when everything is not ideal. That often involves intense emotional response. Do my relationships function under stress? How would I prefer times of financial stress to resolve? Are my personal coping and outlet strategies functioning?
Life Design gives us tools to create qualitative goals and evaluations without becoming victim to our own harsh inner critic or naive optimism.
Possibility vs. Responsibility
When you engage in a life design approach you get to change some of the rules that society and the world have laid out for you. One of the largest of those is the rules of responsibility. Now, just to be clear, I am making a delineation here between responsible for (compelled to influence) and obligated to (agreed to a certain course of action.)
The first books I read on self-help insisted the first thing a person had to do was take responsibility for everything in their life. Win the game? Own it! Lose the pitch? That’s on you! Hit by a bus? That’s on you too! Now don’t get me wrong there is a certain logic to the idea that we should acknowledge our agency in life however limited, but this idea inevitably brings with it a lot of baggage.
In design we get to take a different approach, we get to look at a situation, dissect its successes and failures and design real solutions that are not necessarily based on some perceived weight or framework, but creatively designed to create the life we desire. This ability to deconstruct and re-imagine can be very liberating and actually a rather healthy way to forgive yourself for personal failings and focus on where you want to go next.
How Might Life Migrate Through the Universe?
By the time we realized that there was an extrasolar intruder, ‘Oumuamua, named after the Hawaiian word for “scout,” had already passed its closest point to the Sun and was leaving, as fast and stealthily as it had arrived. We are talking about the first sighting, in 2017, of an asteroid from another area of the galaxy, a messenger from distant worlds. What do we know about this dark, probably cigar-shaped shard, which visited our solar system with a trajectory and velocity that allowed it to leave so quickly?
Very little. We know that it was not made of ice, so it must be of the rocky type. It did not ignite like a comet as it approached the Sun. We know that it does not emit electromagnetic radiation. The most powerful radio telescopes have found no trace of it. Its orbit is gravitational, determined by the attraction of the Sun; a small, non-inertial component can be explained by the effect of the pressure of the radiation in our star’s vicinity. We know that its speed, before entering the solar system, was compatible with the characteristic speeds of celestial bodies in the region of the Milky Way, of which our solar system is part. This allows us to exclude the idea that it comes from one of the dozen stars closest to us, as its velocity would have been too high. However, we have identified four more distant stars near which it could have passed in the last million years, with a velocity low enough that it could have originated in one of these star systems.
So, we don’t know exactly where it comes from, if it has already been in our solar system, how many other systems it has visited, or its composition. According to one hypothesis, it could be a fragment of an exoplanet destroyed by tidal effects. In this case it would be an object much rarer than main belt asteroids or objects from the Oort cloud, which formed directly from the original nebula. What is certain is that, on timescales of the order of millions or tens of millions of years, fragments like ‘Oumuamua can bring different star systems into contact. One estimate even predicts that 10,000 extrasolar asteroids cross Neptune’s orbit on a daily basis.
On timescales of the order of millions or tens of millions of years, fragments like ‘Oumuamua can bring different star systems into contact.
It would be interesting to be able to explore one to see what it was made of. This type of asteroid would seem to be the kind of vector suitable for transporting life, in hibernating form, from one part of the galaxy to another. While a space mission of this kind would be difficult because of the speed at which these fragments are moving, it wouldn’t be impossible, considering that in the future our observational capacity will improve considerably, allowing us to identify these bodies sooner than we were able to identify ‘Oumuamua. Another idea has to do with the possibility that some of these extrasolar objects have become trapped in our solar system after having lost some of their energy in a close encounter with Jupiter; a few candidates have already been identified. This approach would make an exploratory mission much easier to accomplish.
However, even the planets in our own solar system are in communication and exchanging material at a fairly high rate. Not everyone knows that we have about 10 rock samples from Mars here on Earth, even though there has not yet been a mission that brought back material from that planet. The meteorite bombardment on Mars results in fragments that, given its thin atmosphere, can be projected into space. Some of them can reach the Earth, penetrate our atmosphere, and fall like normal meteorites. By comparing the isotopic composition of various meteorites with those measured on Mars during NASA’s robotic missions to the planet, we are able to identify and distinguish Martian meteorites from all the others.
Finally, we should remember that it takes the solar system about 220 million years to revolve around the center of the galaxy. Since it formed 4.5 billion years ago, it has made the full circuit about 20 times. This means that, in the timescale in which life emerged on Earth, the newborn Solar System had many opportunities to come into contact with fragments from distant star systems.
In 2019 I participated in a Breakthrough Discuss conference in Berkeley on “Migration of Life in the Universe.” I was puzzled by the conference theme: We know almost nothing about life in the universe, I thought, so how we could talk about migration of life? But recalling the observation of ‘Oumuamua, I did participate and I am glad I did. I was surprised by the scientific quality of the talks and by the extreme fascination of the topic. Life probably doesn’t need massive, rocky starships to move from one planetary system to another. Considering the minuscule size of bacteria, the smallest living organisms we know, or even viruses, which can live and reproduce inside bacteria, we can also imagine other mechanisms suitable for this kind of transport.
Microscopic ice crystals and dust, for example, containing bacteria and spores capable of withstanding the conditions in space, can spread into space from areas of a planet’s upper atmosphere. When the dimensions become microscopic, the relationship between gravitational force, which is dependent on mass, and the thrust due to stellar radiation, which is dependent on surface area, tips the balance in favor of the latter. It is as if a planet were leaving a trail of perfume behind it. Planetary dust containing hibernating life can be pushed by radiation until it reaches high velocities and moves beyond a given star system, spreading to other systems or nebulae, where it can find suitable conditions to reproduce and evolve. We are used to thinking of space as vast and mostly empty, completely unsuitable for life. Perhaps we should change our minds. Space is less empty than we might think. In reality, the different parts of the galaxy communicate by exchanging material on timescales comparable to those of the appearance of life on our planet.
We know of various living species that can endure extremely hostile conditions such as those in space: a nearly perfect vacuum, extreme temperatures, and ionizing radiation.
But how possible is it for life to survive in space? Well, even here, nature surprises us. In fact, we know of various living species that can endure extremely hostile conditions such as those in space: a nearly perfect vacuum, extreme temperatures, and ionizing radiation. Different kinds of lichens, bacteria, and spores are able to survive, losing all of their water and entering into a condition of total inactivity — which can last for extremely long periods — from which they can emerge, once they find themselves in a humid atmosphere again. Tests of this kind have been done on the International Space Station and in various laboratories. Even plankton, made of more complex organisms, shows a capacity to resist these prohibitive conditions.
A truly extraordinary case is that of the tardigrades. These very common micro-animals are about a half a millimeter long and live in water. They have eight legs, a mouth and a digestive system, as well as a simple nerve and brain structure. They are also able to sexually reproduce. They exist in nature in thousands of different versions and have a metabolism with unique characteristics. In order to withstand prolonged drought conditions, their bodies can achieve complete dehydration, losing around 90 percent of their water and curling up into a tiny, barrel-shaped structure. In other words, it’s as if they freeze-dry themselves. Once this process is complete, their metabolism becomes 10,000 times slower. The most amazing thing is that they can stay in this state for decades, only to wake up again within 20 or 30 minutes once exposed to moisture. But there’s more. When in a dehydrated state, they can withstand the vacuum of space as well as pressures higher than normal atmospheric pressures, temperatures near absolute zero or temperatures up to 150°C. Their radiation tolerance threshold is hundreds of times higher than what would be deadly for humans. The secret of their ability to harden is due to a sugar, trehalose, which is also widely used in the food industry. When dried, this sugar replaces the water molecules in the cells, leaving the animal in a kind of vitrified state.
In addition, the tardigrade’s DNA is protected by a protein that reduces radiation damage. Is this information enough to make us assume that these micro-animals come from space? I would say no. Their unusual metabolism is more likely the result of evolutionary adaptation that happened on our planet. In fact, tardigrades are among the very few living beings that have emerged unscathed from all five extinction events that have occurred on Earth. That is why they are the best candidates for a long journey into space aboard a meteorite or a comet. Recently, tardigrades have achieved a bit of media notoriety resulting from the Beresheet mission, a private probe launched by Israel, that crashed on the Moon in early April of 2019. The probe was carrying a colony of these micro-animals, in their dehydrated state. Given their microscopic size, it is likely that they survived the crash and will remain inactive for a long time to come, ready to be reawakened from their hibernation. By replacing the Israeli probe with an asteroid, we have a textbook example of how life might have arrived on Earth.
Or how life could have migrated from Earth to other planets in our galaxy.
By replacing the Israeli probe with an asteroid, we have a textbook example of how life might have arrived on Earth.
So, the problem of the origin of life remains open, even if, step by step, we are making progress toward a solution. In the last decade, increasingly powerful calculation instruments have allowed us to reproduce, starting from the first principles of quantum mechanics, the formation of increasingly large and complex molecular systems, now made up of thousands of atoms. The field of computational biology is growing at a formidable rate; it is now only a matter of computing power.
At the same time we have dramatically developed our ability to decode and manipulate DNA, up to the creation of the first simplified genomic structures, derived from living organisms and able to reproduce. We are now talking about synthetic life, built around human-designed DNA, a field with huge development prospects.
Therefore, it is likely that the creation of the complex molecular structures needed for life or the confirmation of the existence of islands of genomic stability in the evolution of viral and bacterial species are objectives that, in future, will be within our reach. At that point, we will have another tool for understanding how life on Earth developed. Who knows? Perhaps we will discover that aliens are particular biological life forms that have lived with us since the beginning of time; and we were looking for them on Mars or below the icy surface of Jupiter and Saturn’s moons!
Roberto Battiston is a physicist who specializes in the field of experimental fundamental and elementary particle physics, both with particle accelerators and in space. He is the author of several books, including “First Dawn,” from which this article is excerpted.
