Climate Change - The Point of No Return

We are on the verge of rendering our planet uninhabitable, unless drastic action is taken.

Scientists have recently announced, quite alarmingly, that climate change on our planet could soon reach its tipping point. We are only decades away from that moment. It will happen within a generation.

Lowering our carbon dioxide emissions is no longer enough. Carbon dioxide needs to be extracted from the atmosphere. And we need to start doing that now on a large scale. Otherwise, global warming will enter an unstoppable feedback stage, where warming triggers more warming, which triggers even more warming. Such feedbacks include the release of methane due to the thawing of permafrost, loss of snow cover, the melting of Arctic ice, warming seas, and the loss of forests. All of those will reduce our planet's ability to reflect heat and absorb carbon. The number and intensity of forest fires will increase dramatically, releasing huge amounts of greenhouse gases into the atmosphere. This will only magnify the feedback effect even more.

Global warming will result in an increase in the frequency and ferocity of forest fires. Such fires add vast amounts of greenhouse gases to the atmosphere.

The end result of such warming is not clear, but at best it will significantly limit the areas of the Earth where humans can comfortably survive. At worst it will render the whole planet uninhabitable, water will boil away, and the Earth will suffer the same fate as Venus,

Even the 'best case' scenario will cause massive migrations, and subsequently major wars over dwindling food, water and energy resources. Such wars will only add to the warming feedback. As the desperation of governments increases those with nuclear weapons at their dosposal will eventually use them. Countries such as Israel, India, Pakistan and Iran - all nuclear powers and all located in what will become some of the worst affected regions - will feel compelled to use such weapons as countries to their north attempt to stop the migration of their populations. This will cause tremendous damage to the environment, and render even more areas uninhabitable. And there would be a very high chance that a limited nuclear war would escalate rapidly into a global nuclear conflict.

At that point our current technological civilisation will end, and with it humanity's chances of spreading beyond the Earth to become an interplanetary, and then an interstellar, civilisation. Our ability to preserve our species will have slipped away.

If he climate change wars turn into nuclear conficts they will bring to an end our current technological civilisation. Humans may have a change to develop another advanced civilisation one day, but it is likely to take centuries or even millenia to get back to anything like that which we have achieved today. Without forewarning such a civisation is almost certainly doomed to suffer the same fate as the one before it.

Such a dramatic warming of the atmosphere will cause a rapid rise in sea level, raising it to well over a hundred metres higher than it is at present. In addition to the billions who had already perished in the wars of the previous decades, hundreds of millions more will die. Survivors, who will eventually number just a few tens of million at best, will struggle to live in the few remaining higher altitude lands. Their existence will be basic and medieval. It will be a return to the dark ages. Thousands of years of progress and knowledge will have been lost.

Only then, with the destructive output of our current civilisation at an end, can the climate of Earth have a chance to stabilise. The ice caps will reform and the sea level will reduce. After many centuries flora and fauna will start to recover. Only at that point, humans, if they are not extinct, will have another chance at building a technologically advanced civilisation.

It's unlikely that we can prevent a climate change disaster on our planet, but we can improve on the 'best case' scenario if we start doing three things right now:

1. Preserve Knowledge of our Discoveries and Inventions

We must help survivors in the post-climate change world avoid repeating our calamitous mistakes, and allow them to 'fast-track' through what has taken our current civilisation thousands of years to learn, discover and invent.

A comprehensive record of our achievements (and of our destructive actions, so that mistakes are not repeated), must be preserved in a way that they can understand, and in a way that will last for thousands, even millions, of years. We must investigate how we can provide such knowledge to our distant descendants, and then store it in multiple safe yet easily accessible locations, including locations elsewhere in the Solar-System.

DNA could be the ideal solution to extremely long term information storage

Using paper or digital media to preserve knowledge will only be suitable for a few hundred years or so, but such means should be used initially, as our descendants will be able to understand and use these forms of storage.

But a more radical solution is needed for complex and advanced knowledge that will be useful once any new civilisation progresses to a certain level. Storing information in DNA is one such solution. It's been shown that if the DNA can be kept at sub-zero temperatures the information will maintain its integrity almost indefinitely. DNA information stores would be best located away from Earth, perhaps on the Moon in the permanent darkness of one of the polar craters, and deep within some of the planetary bodies of the outer Solar-System.

2. Work to Avoid or Delay the Climate Change Tipping Point

Even to just delay the tipping point we need to start work now.  The small steps some of us are currently taking are utterly inadequate.

Our civilisation needs to fast track the very widespread use of electric vehicles by banning petrol and diesel engines within a decade. All developed countries need to push this idea hard, and give incentives to developing countries to do the same. And governments need to increase vastly the funding for research into clean energy, and get nuclear fusion working. The generation of electricity by burning coal and oil has to stop on a worldwide scale without delay. Countries like China appear to be increasing the use of fossil fuels for energy generation, which is going to be catastrophic if it is not prevented.

But that alone will not be enough. We need to start undoing the damage we've already done.

Various climate engineering projects should be started immediately. These are possible with current technology. To help reduce global warming solar radiation management needs to be implemented to reduce the sunlight absorbed by the atmosphere. Relatively simple things can be done such as seeding clouds with sea water to brighten them (and therefore reflect more sunlight), and using pale roof colourings and promoting the expansion of polar ice.

Removing carbon dioxide from the atmosphere using facilities such as this is possible. It can be stored in hard pellets which can be buried deep underground.

We need to start removing some of the excess greenhouse gases that our activities have pumped into the atmosphere. This can be done directly using machinery that would then store the extracted carbon dioxide deep underground, and indirectly by promoting natural processes, such as extensive tree planting to reverse deforestation, and ocean fertilisation to add nutrients to the upper oceans to increase carbon dioxide absorption.

And the growth of our human population needs to be controlled, especially in developing countries. We can no longer support such large increases, which are generally located in regions that can least support it. It should be stabilised as soon as possible, and allowed to reduce naturally to a more sustainable level.

Doing all of the above is the best chance the Earth has of remaining a viable place for humans to live. But it is likely to only buy us some time - nothing more. We need to establish our civilisation elsewhere to properly secure our future.

3. Secure the Survival of Our Civilisation Independent of Earth

There's a significant possibility that the feedback warming will not stop, and if that is the case the Earth could indeed end up in a state similar to that of Venus.

The only way to ensure the continuation of our species beyond that event is to make sure that there are self-sustaining human colonies beyond Earth, on planetary bodies such as the Moon, Mars, and especially on what is looking like the best location: Titan, the largest moon of Saturn.

As well as colonies on planetary bodies there should be very large space habitats constructed throughout the Solar-System that would house tens of thousands. The resources to build such massive facilities can be found in the asteroid belt between Mars and Jupiter.

We will have to mine asteroids on a large scale to construct the off-world facilities humans will need to live independently from Earth

Extracting those resources would be relatively easy due to the very low gravity wells of the asteroids. The establishment of mining operations there must be an immediate priority. The space habitats could be constructed in the asteroid belt and then maneuvered into their final positions, either into planetary orbits, or into their own independent orbits around the sun.

In parallel to the development of colonies around the Solar-System there needs to be development of interstellar missions with the goal of establishing human colonies around other stars. More and more exo-planets with the potential for colonisation are being discovered all the time, with one, Proxima Centauri B, only 4.3 light years away.

The planet Proxima B, which orbits Proxima Centauri 4.3 light-years from Earth. It's the closest known Earth-like exo-planet, and has huge potential as a suitable destination for our first interstellar colonisation mission.

It would be a mammoth undertaking, and there are incredible engineering challenges to overcome, but investment in the rapid development of the methods and technology required is essential to build such habitats in time. As well as providing immediate funding, it should be the priority of governments to ensure that education systems are geared to maintain a constant supply of highly capable scientists and engineers to make it a success. The long term survival of our species depends on it.

If all three of the above steps - preservation of our knowledge, delaying or avoiding the tipping point, and establishing large self-sustaining human colonies elsewhere in the Solar-System and beyond - are pursued with the resilience, determination and creativity that our species has in abundance, then we will survive.

But we must start now.

Right now.

Uranus Mission: Essential and Urgent

Of the larger planets in the Solar-System, Jupiter and Saturn, and their moons, seem to get almost all of the attention when it comes to orbiter and lander missions. That's understandable, of course. There's a huge amount of fascinating bodies in those systems, and many mysteries to solve and theories to prove. And the fact that those systems are relatively easy to get to helps.

But a mission dedicated to Uranus and its system of moons is long overdue.

The planet Uranus: the coldest planet in the Solar-System

Since 2010 there have been five proposed missions to Uranus. These have been by the United Kingdom (Uranus Pathfinder), ESA (MUSE and ODINUS) and NASA (Oceanus and NASA Uranus Orbiter and Probe). It’s disappointing that none of them has yet been given the go-ahead, and none of them are likely to be given it due to budget constraints and the priority given to other missions, particularly those to the Jovian system.  Even if one or more of the Uranus missions was given the go-ahead, the earliest any of them would arrive at Uranus would be the mid to late 2030s (with ODINUS not even launching until 2034).

A Uranus orbiter and atmospheric probe

There is clearly the need for much more urgency and ambition. And there is a need to use a means of getting to Uranus that does not require a cruise time of up to 15 years (due the requirement for coventional rocket propulsion to make use of multiple gravitational slingshot maneuvers using Venus, Earth, Jupiter and Saturn). A more advanced method of propulsion is required: one that is much more powerful and sustained than current rocket technology. Nuclear thermal rockets, which have been developed and tested for decades, but never used, would allow for an orbiter mission to be launched on a direct trajectory to Uranus. The journey time would be reduced to just a few years.

But why would there be such an urgency to get an orbiter mission all the way out to Uranus so quickly? It's simply because there are many mysteries about the planet that need answers. And the sooner we know those answers the better.

One of the major mysteries about Uranus is that, unlike the other planets in the Solar-System, it seems to generate almost no heat at all. There seem to be no reasonable explanations as to why. It's quite possible that the heat energy could have been extracted from the planet by some extreme geo-thermal power generator. Indeed, the planet's unusual axial tilt, which makes the planet appear as if it's laying on its side compared to the Solar-System's other planets, and its magnetic field, which is at an extreme tilt in relation to the planet's rotation and is also off-centre by quite a margin, all point to unusual and potentially unnatural events that occurred as the planet's resources were utilised.

There is a likelihood that long ago the Uranian system was the location of some intense activity by an ancient extra-terrestrial civilisation: perhaps from Venus or Mars, or maybe even from Earth many millions of years ago (see my article 'Pre-Human Technology in the Asteroid Belt'). A vast engineering project of some kind may have been implemented. The evidence of such activity, even if it ceased hundreds of millions of years ago, will still be there for us to discover. We need to know what was going on, and why.

The most likely place we'll find that evidence is on the planet's moons.

Miranda, the smallest and innermost of the major moons of Uranus

The moons would provide all the resources needed for a civilisation as it worked. The moon Miranda, the smallest of Uranus' major moons, certainly has the appearance of a moon that has been heavily mined. As it's composition is mainly water ice its surface could have been the main source of water, oxygen and hydrogen for fuel.

The planet's largest moons, Titania and Oberon, do not show signs of mining, but they would make ideal locations for habitats and deserve detailed surface investigations. Ulimately, a strong human presence is required for a thorough investigation (and of course for the more general reason of helping ensure the survival of our species if/when something catastrophic occurs on Earth).

At the very least, a human colony in the Uranian system would be an ideal base from which to explore the outer Solar-System.

Human colonists on Miranda enjoying ultra-low gravity recreational activities 

A small human outpost on Titania, the largest moon of Uranus

An orbiter mission to Uranus and landers for its moons are essential. Sooner rather than later we need to know what happened in the Uranian system. And ultimately we need to establish a permanent human presence there to help ensure our long-term survival.

Human Colony on Titan

Titan is Saturn's largest moon (and the second largest in the Solar-System after Jupiter's moon, Ganymede). It is unique in many ways, most notably for its thick atmosphere, weather patterns, including rain, and its lakes and rivers. It is one of the best places in the Solar-System for a large human colony. It has the potential to support millions, in fact.

And there is, of course, the potential to discover a completely different form of life and biology to that of our own.

Saturn's largest moon, Titan. Left: a true colour image. Right: overlaid with an infra-red view of the surface.

Here's why Titan would be a promising place to build a colony:

• Titan's thick atmosphere and air pressure, that's just above that of Earth's surface, would eliminate the requirement for bulky pressure suits. A suit would simply need to provide warmth and oxygen.
• The hydrocarbon lakes would provide the materials to make plastics that could be used to make all the required structures for living and working.
• The atmosphere would provide excellent protection from radiation and meteorites, and make any leaks or failures of habitats a problem rather than a lethal failure (the indoor and outdoor pressure would be the same and therefore any leaks very slow).
• Drilling into the surface would provide all the water a colony could ever want. And from that could be extracted oxygen, and hydrogen for fuel.
• The low gravity would make return to space relatively easy, and the thick atmosphere would make aircraft particularly easy and economical to fly. Human-powered flight is possible.
• If there is any life on the surface of Titan it is likely to be methane-based, which should mean it would be unable to survive in a human environment. The danger of either life-form infecting the other would be minimal. It's very likely they could coexist without any problems.

There are significant challenges to overcome, but none are in any way insurmountable:

• The surface temperature is extremely low at about -180 degrees Celsius. This is significantly colder than even the coldest locations on Earth. New types of clothing and insulation will need to be developed to cope with this.
• It is currently unknown exactly how detrimental to health living in such a low gravity environment would be. Those born and raised on Titan may well be unable to leave the moon due to the weakness of their bodies. They would certainly never be able to visit Earth.
• The journey time from Earth to Titan would be many years using conventional rocket technology. Unless the ship had a rotating section to generate artificial gravity, and effective radiation protection, the crew would suffer significant health issues. Nuclear propulsion would significantly reduce journey times (this has been researched heavily but never used).
• There is a possibility of water-based life existing in the subsurface oceans. The water extracted for use by the colonists would need to be thoroughly studied and sterilised to prevent contamination and infection.

A view of Titan's surface from an altitude of 70 kilometres

Creating a Self-Sustaining Colony

Landing on airless moons is always problematic due to the need to rely solely on rockets to slow down enough for a safe landing. A large amount of fuel needs to be transported each time. No such problem exists at Titan. The thick atmosphere and low gravity of the moon makes it easy to take advantage of aerobraking techniques and relatively small parachutes (compared to the large parachutes that would be required in the thin atmosphere of Mars).

Because of this very large landing craft, carrying hundreds of tonnes of cargo, or even hundreds of colonists, should be able to land quite easily.

Before colonists arrive in large numbers a sizeable 'town' of habitats will be needed, with power generation and crop growing facilities to enable self-sufficiency. It needs to be well planned, with plenty of redundancy, factories (making use if the liquid hydrocarbons), and with roads and airstrips, and space launch facilities.  There will be no chance of rescue for a colony so far from Earth.

The initial habitats will have to be sent by unmanned missions. They will be built robotically. The first humans will then arrive to expand the facilities and establish what will become the first self-sustaining colony. It's likely that this initial stage would take two or three decades to complete. Essentially, the first generation of colonists would be living in a frontier town, with limited but slowly improving comforts.

A shuttle takes off for a journey to an orbiting station around Titan. Once the colony matures and fuel and manufacturing factories are established there will be regular trips to and from the moon's surface to other colonies in the Saturnian system.

The second and future generations would benefit from the growing colony, with spacious homes, more recreation time, and a growing system of orbital facilities to support life on the surface including communications, and transit to and from the surface and to other colonies that will no doubt have been established elsewhere in the Saturnian system and beyond.

At this point, when survival is routine rather than the main task of each colonist each day, research and scientific discovery can take priority. And it will no doubt focus on the indigenous life that is quite possibly abundant on the moon. Such life could well be complex, with the lakes especially teeming with larger creatures that are just impossible to detect without a surface presence.

A large methane-based complex life-form living in one of the hydrocarbon seas on Titan. The actual life on Titan is likely to be less extravagant than that shown in this image, but it still could have evolved into an array of sizeable creatures.  

Titan could have a diverse ecosystem, far removed from what we know here on Earth. It is the most exciting location in the Solar-System to look for life. There will be no shortage of scientists willing to live there when the time comes to send them.

Robotic Exploration

Before any human colonisation of Titan can start we need to know much more about the moon and its surface conditions. We must send surface exploration missions there at the earliest opportunity.

Some missions have been proposed since 2008, such as the Titan Saturn System Mission. It's an ambitious proposal consisting of an orbiter, a balloon to explore the atmosphere and photograph the surface, and a lander that would splash down in one of the methane lakes.

Another proposal is the Titan Mare Explorer. It's a relatively low cost mission that would put a lander on one of Titan's seas. Unfortunately it did not receive funding, but the lander could end up as the lander for the Titan Saturn System Mission if that ever gets off the ground.

Kraken Mare, Titan's largest sea, seen from a high altitude. NASA is researching the possibility of sending a submarine to explore the sea's depths. If it goes ahead it would be a remarkable mission, and one that has the potential to encounter what could be a complex ecosystem of methane-based life.

Flying in Titan's atmosphere is easy due to it's high density and the moon's low gravity. AVIATR proposes sending an aeroplane that would spend a year flying aound Titan, before attempting a landing. And there is ongoing research into a submarine that would explore Kraken Mare, the largest sea on Titan.

None of the above proposals are ever likely to launch. But there is a proposal that has a reasonable chance of getting full approval. Dragonfly, as it is known, would send a rotorcraft (similar to a quadcopter drone) to explore the moon. It would have the ability to fly at speeds up to 10 metres per second and reach altitudes of up to 4 kilometres. It would land and recharge from its radioisotopic generator during Titan's long nights. While landed it would sample the surface composition. It’s an ambitious and cost effective proposal.

The Dragonfly drone: an essential mission to Titan, and one that could be launched in the next decade

In July 2019 NASA will select either Dragonfly or CAESAR (a comet sample and return mission) for launch in the mid 2020s.

Titan's huge importance cannot be stressed enough, both to help ensure the future of our species by being one of the best places for a sustainable human colony, and by being the likely home of a completely new form of life.

Both of those reasons must ensure that Dragonfly is chosen.

They simply must.

Should All Interstellar Missions Be Silent?

The first detected interstellar object passed through the inner Solar-System last year, and is now heading away back to interstellar space. Named 'Oumuamua', the object, approximately 230 metres in length and around 30 metres wide, reached a speed of almost 88 kilometres per second at its closest approach to the sun.

Oumuamua: an interstellar object that passed through the inner Solar-System in 2017. It is potentially a camouflaged extraterrestrial embryo colonisation starship making use of our sun for a gravitational course correction.

There's a reasonable possibility that the object is artificial. It could be an interstellar colonisation mission that is using our sun to provide a gravitational  course correction, putting it on its final trajectory for its target star system, or setting itself up for another gravitational course correction in tens of thousand years time. And it could well have made some passive observations of our planet on the way through.

The object is too small to be a generation ship. A ship many times larger would be required to allow thousands of beings the chance to live and breed for many millennia as their voyage unfolds. But the ship is certainly large enough to be what is arguably a more efficient means of interstellar colonisation: an embryo ship. Such a ship would need to be much more advanced, requiring artificial wombs, and artificial 'parents' and educators. If Oumuamua is indeed such a vessel then it would be a remarkably complex technological marvel, and something worth pursuing when we have the means to do so.

On board an embryo star-ship a human colonisation crew is grown in artificial wombs

A lot of effort was made to detect signals from Oumuamua. None were detected. But why should any have been? Such an interstellar ship, with embryos only, would be fully automated, with no sentient crew (apart from perhaps an overseeing artificial intelligence). There would be little reason for the ship to make a transmission home, except during the safe interstellar phases of its voyage. Even if it did, it would be a very directed and focused transmission that would not hit our planet. And using stars such as our sun to provide course alterations would almost eliminate the need to use a means of propulsion, the emissions of which would be detectable, while transiting the system.

Maintaining a strict 'silent running' policy is essential for all pioneering interstellar missions. Only very targeted and rare encrypted transmissions to the home world should be made, and only when the ship is well away from possibly inhabited star systems. The rest of the time a starship should appear, apart from during the very closest of inspections, as a natural object. Any course corrections using a propulsion mechanism must only be made in interstellar space.

This seems to be the most sensible approach for us when we finally embark on colonisation missions to other star systems. And I would expect it's the approach taken by extraterrestrial civilisations that are already undertaking such voyages. That would certainly explain why we are not detecting any transmissions. Such strict controls are obviously being maintained during voyages, and when colonies are established. And such controls are no doubt being enforced on home worlds.

It's very likely that, at this point in time, our civilisation is one of the very few (even the only one) in our region of the galaxy allowing unregulated transmissions without considering how visible we are to civilisations in the surrounding star systems.

Listening for signals from extraterrestrial civilisations is a good idea. But is it wise to also transmit messages in the hope that one of them receives it? Perhaps we have not detected any civilisations because they have a good reason to keep quiet. Maybe we should, too...

This could possibly be to our advantage. It could act as a warning that our star system is home to a reckless species that does not care what it does, and who knows about it. It could make potential invaders think again and head for a quieter system.

Or more likely it could act as a sign that we are an undeveloped and ignorant species, unaware of the risks of attracting attention. We could be considered an easy target for eradication, and Earth as an easy project for redevelopment. Or we could simply be 'silenced' to prevent us bringing to this region the malevolence other civilisations fear.

We have only been transmitting radio signals for just over a century. That is not really enough time for any alien civilisation to analyse those signals and complete a voyage here. But there are already many star systems identified within a hundred light-years of our planet that could host life and even advanced civilisations. Our unfettered radio transmissions could have been detected decades ago.

If such a civilisation is advanced enough to already have starships constructed then it may not take much effort or time to prepare and direct one this way.

Extra-terrestrial visitors may well be friendly, but we should also be prepared for a hostile encounter

An interstellar ship or probe could be on its way to us right now. If it's able to reach speeds that are a significant percentage of the speed of light it could arrive by the turn of the century. We need to take seriously the possibility that an extraterrestrial civilisation has found us. 

They may be heading here right now.

It would be wise to prepare for an encounter with them within the lifetimes of those born today. We should hope that they are benevolent, and be ready to greet them as friends.

But we need to plan for the possibility that they are not.

Comfortable Homes on Mars

Mars is one of the most likely places in the Solar-System where the first permanent human colony away from Earth will be established. With the right equipment the planet has all the resources required to sustain a community indefinitely. And there is also the intriguing possibility of discovering evidence of an ancient technological civilisation that once existed on the planet.

Before the search for such evidence can begin there are practical issues that need to be addressed. Habitats with enough space and comfort are required to maintain the physical and mental health of the colonists. And such space and comfort should be ready and waiting even for the very first colonists to arrive. They will need decent quality homes, with enough comforts to get them through the months and years before they have the opportunity to return to Earth. Those habitats should be nothing less than a home from home.

There are plenty of designs for such habitats, but NASA's ice home concept is one of the more practical and impressive ones.

NASA's Mars ice home. The inside is inflated and then the outer shell filled with water. It can be constructed robotically and be ready when astronauts arrive.

The home consists of an inflatable torus within which there are two levels of living space comparable to that of a small house on Earth. The torus is surrounded by chambers filled with ice to provide insulation and radiation protection. The water for the ice will be extracted from the subsurface ice that is abundant in many locations on Mars. Because of this the actual structure itself is very lightweight and can be deployed and build robotically. The homes would be delivered to Mars and prepared over the span of a year or so. When humans finally arrive they'll be able to move immediately into comfortable habitats.

A cross-section of NASA's ice home showing the interior space

Whatever the design of the house, its interior should offer the ocupants the comforts of a home on Earth. It should be a familiar and safe place to return to, with space to relax and have privacy when required.

The first humans visiting Mars will almost certainly face a stay of at least a couple of months, and possibly a year or two.  And that would be after many months of arduous travel in a cramped spacecraft. It is vital that those humans are provided with all the normal comforts possible to allow them to recover physically and mentally: essential for them to do their work effectively, and also for them to prepare for their return journey.

The interior of a house on Mars should offer all the comforts of a home on Earth. It should be spacious, clean, bright, and be familiar and cosy.

Such homes should last many years, and be ideal for the early missions. But ultimately they would be temporary. One day people will arrive on Mars who will never leave. And soon after that the first children will be born there. By that time a substantial and permanent habitat will need to have been constructed.

Space X Mars surface colony circa 2050 with a busy spaceport. Large numbers of human are arriving as the construction of permanent habitats continues. Many of those arriving at this time will never leave, and many will start families there.

The best place for permanent homes is below ground, or inside hills and mountains. Excavating such facilities from scratch would be an immense undertaking, but utilising existing underground chambers, such as lava tubes, would reduce the workload significantly. Homes for thousands could be build in such tubes, and the thick shielding required by surface habitats would not be necessary as the roof of the tube would be more than adequate.

A colony set up in the relative safety of a lava tube on Mars

As well as exploiting natural underground voids such as lava tubes, there is the possibility to exploit unnatural voids, too (see my previous articles 'Sanctuary Entrance Found on Mars' and 'Where Did All the Martians Go?'). The search for such 'unnatural' voids is, in my opinion, one of the two primary reasons for sending humans to Mars (the other being, of course, to aid in the survival of our species if and when a global catastrophe occurs on Earth).

There is strong evidence to suggest that Mars was once a temperate world: one that could have been a perfect environment for life to thrive. That environment was likely to have existed for more than a billion years. That's more than enough time for an advanced civilisation to develop. For whatever reason that life-nourishing environment began to fail. It could not be saved. If there was a Martian civilisation it would have had no choice but to retreat underground (with a privileged few managing leaving the planet). 

Eventually the underground civilisation would have died out.

Colonists on Mars explore the remains of a long dead underground Martian city

Many of the vast chambers and warrens of tunnels they constructed must still remain, ready to be exploited when our civilisation arrives on the planet. There may be huge networks of structures and dwellings that could be modified for human habitation. Within just two centuries there could be a population of millions of humans living on Mars with complete independence from Earth.

When the first humans arrive on Mars and have their first colony up and running they must begin the search for those underground chambers. And from where better to embark on that search each day than a safe, spacious and pleasant home with all the familiar comforts of Earth.

Secret Colonies Beween the Stars

We tend to think of human colonies beyond Earth as being located on planets or moons around stars. The abundant energy resources at such locations certainly make such thinking logical and sensible.

But such locations are also the most visible and desirable. And that makes those locations the most likely places where we may encounter a competing and hostile civilisation.

While we should certainly colonise other star systems, we should also consider colonising deep interstellar space. We should create clandestine colonies; ones that limit contact with the star-bound colonies. Those clandestine colonies would need to be large and self-sustaining, and most importantly  they would need to be 'silent', with no emissions, including light, detectable from even just a single light-year away.

A clandestine interstellar habitat under construction. A rogue asteroid is used to provide the resources required.

Such colonies would be our insurance. They would passively monitor the surrounding human colonies, watching and listening for signs of distress. They would ensure our continuation as a species should our star system colonies suffer natural or unnatural catastrophes.

In an earlier article titled 'Living on Rogue Planets' I explored how life could evolve on planets between the stars, how humans could colonise them and reasons why such planets would be safe from various threats. But finding such worlds would be difficult, and they would be unlikely to be in the right locations. It would be better to create our own rogue worlds in exactly the locations we want, and where they would not drift close to star-systems for millions of years.

Simply put, the clandestine colonies must be located in the right places to be able to remain hidden essentially forever.

But how could such remote colonies be created and sustained?

One possibility would be to create generation starships that would intentionally 'stop' in the void between stars. Such spacecraft would,  of course, need to have very efficient and self-sustaining ecosystems and the means to provide appropriate energy generation. This could be fusion-based, or even antimatter-based. This would provide enough energy to create the light and warmth for growing food to maintain a significant human colony.

Resources would be required for manufacturing replacement parts, new equipment and topping up air and water supplies. Comets from the very outer reaches of star systems (such as the Oort Cloud in our Solar-System) could be redirected to pass close enough to the clandestine colonies to be easily mined.

A comet in the Oort Cloud is moved closer to the clandestine human colony nearby. It's resources will help sustain and grow the colony for centuries or more.

Such redirection would be relatively easy as objects in the Oort Cloud are very loosely bound to the sun due to their vast distance. Those objects are essentially just a nudge away from being truely interstellar.

Of course, the Oort Cloud itself is about one to three light-years from the sun, which puts it in interstellar space. This would enable some interstellar colonies to remain shrouded in darkness and secrecy while having access to a sparse but relatively abundant set of resources.

The Oort Cloud in relation to the rest of the Solar-System and its closest neighbouring star-systems. It would be an ideal location for secret human colonies, with relatively easy to find resources from the mass of comets in that interstellar region.

If such clouds of objects are common around most stars it would make setting up such colonies much easier. It should be an essential component of any interstellar colonisation missions that humans embark upon.

Creating sustainable colonies between the stars will be a formidable task, but it is a crucial one. Those colonies will be our backup, and the skills learned by those surviving (and hopefully flourishing) there will be invaluable as the human species spreads throughout the galaxy and beyond.

Time Travel: Travelling Without Moving

One thing that seems to be almost completely overlooked when time travel is discussed, or used within a work of fiction, is location (the only example I can find that mentions it is this Dilbert cartoon strip).

This is a critical omission.

If someone was to go backwards or forwards in time just one minute they would not find themselves standing in the same place on Earth in relation to their original surroundings. They would most likely find themselves many kilometres up in the air, or embedded in rock deep underground. This is because the Earth is rotating and moving through space at many thousands of kilometres per hour as it orbits the sun, which is also moving in relation to the center of our galaxy, and so on.

The classic image of a time machine: something a person could sit in, type in a date, and then travel to that time at that particular location on the surface of the Earth. But the problem with this concept is that the Earth would not be in that location at the destination time period.

To put it simply, we are constantly moving, and so travelling in time will mean we travel to a time before the Earth was in its current location, or to a time after it has moved on. If someone travels in time just a few days they will find themselves millions of miles from Earth in deep space. If they time-travel a couple of decades they will find themselves far beyond the Solar-System in interstellar space.

Time travellers waiting to enter the machine that will send them through time. If such a machine was possible the travelers would need to be on board a spacecraft as they are likely to emerge in deep space. This is a point never considered in fiction.

But the issue of location should not be viewed as a problem. Far from it, in fact. It should be viewed as a major advantage. If we can eventually master time travel in some form it could well be the easiest and fastest way to travel interstellar distances, if only along the path the Earth will take, or has taken.

It's an incredible prospect. But can it ever be possible?

Travel into the future can be achieved, in principle, using the time dilation effect described in Einstein's theory of relativity by travelling close to the speed of light. Travelling to the past would require velocities that exceed the speed of light. This is theoretically possible using cosmic strings, wormholes, or an Alcubierre drive. A huge amount of energy would be required, which would need exotic matter, particularly matter with negative mass. It's all very complicated, and not well understood. But our understanding will improve in this area, as it always does. Sometime over the next few centuries the generation and control of such vast amounts of energy may well be harnessed, and then a device that would enable time travel could be constructed.

Assuming such a device could be built, perhaps in the form of a large orbiting facility that could transport large spacecraft across time, what would be the best way to use it?

An orbiting time portal, capable of transporting large spacecraft to other times

Sending a human crew through such a portal would be an immense undertaking.

Such an expedition would essentially be a one way trip to an unknown destination, with no possibility of return or help once the journey had begun. The spacecraft would need to be interstellar in nature, with the ability to sustain its crew and passengers for decades if necessary, as there would be no way of knowing how close a viable planet would be at the time of arrival. At best we could target the vicinity of an appropriately aged star system that we think has a good chance of hosting an Earth-like planet. And due to the impossibility of knowing the conditions of any planet found for colonisation, the ship would need to contain all the resources required to land and set up a colony in a variety of climate conditions.

However successful the mission is, no one left on Earth is likely to ever know about what happened.

If we just want to ensure the continuation of Earth life we could simply send thousands of probes to different times along the Earth's journey path and have them 'seed' the most Earth-like planets they find with the building blocks of Earth life. One day, a billion years later, perhaps a technologically advanced species would evolve on some of those worlds, an incredibly distant relative of our species.

A probe, sent through time to seed suitable planets with Earth life, arrives and begins observations

I use term 'simply' in a relative sense as this kind mission would still be difficult and complex. The probe's would have to be smart, with artificial intelligence beyond what is currently possible. They would need to observe and detect the most suitable planets or moons within their range, plot and execute a suitable trajectory, and despatch their payloads without any help from scientists on Earth.

Perhaps there are civilisations out there right now based on Earth life, evolved from simple life forms sent back through time by our descendants. If we do eventually master time travel then perhaps we go on to seed worlds a billion or more years ago, when other galaxies occupied our location. Perhaps a bipedal species, reptilian, mammalian or avian (or something extraordinarily different), will one day build a time portal to send explorers to our galaxy.

Perhaps they will find Earth and the ultimate origin of their species.

Or perhaps they will seed Earth and be the origin of ours.