We have comets and asteroids to thank for Earth’s water, according to the most widely-held theory among scientists. But it’s not that cut-and-dried. It’s still a bit of a mystery, and a new study suggests that not all of Earth’s water was delivered to our planet that way.
For almost two decades, NASA’s Earth Observatory has provided a constant stream of information about the Earth’s climate, water cycle, and meteorological patterns. This information has allowed scientists to track weather systems, map urban development and agriculture, and monitor for changes in the atmosphere. This has been especially important given the impact of Anthropogenic Climate Change.
Consider the animation recently released by the Earth Observatory, which show how the city of Cape Town, South Africa has been steadily depleting its supply of fresh water over the past few years. Based on multiple sources of data, this illustration and the images it is based on show how urbanization, over-consumption, and changes in weather patterns around Cape Town are leading to a water crisis.
These images that make up this animation are partly based on satellite data of Cape Town’s six major reservoirs, which was acquired between January 3rd, 2014, and January 14th, 2018. Of these six reservoirs, the largest is the Theewaterskloof Dam, which has a capacity of 480 billion liters (126.8 billion gallons) and accounts for about 41% of the water storage capacity available to Cape Town.
All told, these damns collectively store up to 898,000 megaliters (230 billion gallons) of water for Cape Town’s four million people. But according to data provided by NASA Earth Observatory, Landsat data from the U.S. Geological Survey, and water level data from South Africa’s Department of Water and Sanitation, these reservoirs have been seriously depleted thanks an ongoing drought in the region.
As you can see from the images (and from the animation above), the reservoirs have been slowly shrinking over the past few years. The extent of the reservoirs is shown in blue while dry areas are represented in grey to show how much their water levels have changed. While the decrease is certainly concerning, what is especially surprising is how rapidly it has taken place.
In 2014, Theewaterskloof was near full capacity, and during the previous year, the weather station at Cape Town airport indicated that the region experienced more rainfall than it had seen in decades. Over 682 millimeters (27 inches) of rain was reported in total that year, whereas 515 mm (20.3 in) is considered to be a normal annual rainfall for the region.
However, the region began to experience a drought in 2015 as rainfall faltered to just 325 mm (12.8 in). The next year was even worse with 221 mm (8.7 in); and in 2017, the station recorded just 157 mm (6.2 in) of rain. As of January 29th, 2018, the six reservoirs were at just 26% of their total capacity and Theewaterskloof Dam was in the worst shape, with just 13% of its capacity.
Naturally, this is rather dire news for Cape Town’s 4 million residents, and has led to some rather stark predictions. According to a recent statement made by the mayor of Cape Town, if current consumption patterns continue then the city’s disaster plan will have to be enacted. Known as Day Zero, this plan will go into effect when the city’s reservoirs reach 13.5% of capacity, and will result in water being turned off for all but hospitals and communal taps.
At this point, most people in the city will be left without tap water for drinking, bathing, or other uses and will be forced to procure water from some 200 collection points throughout the city. At present, Day Zero is expected to happen on April 12th, depending on weather patterns and consumption in the coming months.
Ordinarily, the rainy season last from May to September, and the implementation of Day Zero will depend on the level of rainfall. By the end of January, farmers will also stop drawing from the system for irrigation, meaning that water supplies prior to the rainy season could be stretched a little longer.
This is not the first time that Cape Town has been faced with the prospect of a Day Zero. Back in May of 2017, the city was declared a disaster area as the annual rainfall proved to be less than hoped for. This led to the province instituting the Disaster Management Act, which gives the provincial government the power to re-prioritize funding and enact conservation measures to preserve water in preparation for the dry season.
By the following September, Cape Town authorities released a series of guidelines for water usage that banned the use of all drinking water for non-essential purposes and urged people to use less than 87 liters (23 gallons) of water per person, per day. At the same time, authorities indicated that they were pursuing efforts to increase the supply of water by recycling, establish new desalinization facilities, and drill for new sources of groundwater.
But with the drought going into it’s fourth year, there is once again fear that the water crisis is not going to end anytime soon. According to an analysis performed by Piotr Wolski, a hydrologist at the Climate Systems Analysis Group at the University of Cape Town, this sort of pattern is something that happens every 1000 years or so. This conclusion was based on rainfall patterns dating back to 1923.
However, population growth and a lack of new infrastructure in the region has made the current water crisis what it is. Between 1995 and 2018, the population of Cape Town grew by roughly 80% while the capacity of the region’s dams grew by just 15%. However, the current predicament has accelerated plans to increase the water supply by creating new infrastructure and diverting water from the Berg River to the Voëlvlei Dam (now scheduled for completion by 2019).
For people living in many other parts of the world this story is a very familiar one. This includes California, which has been experiencing annual droughts since 2012; and southern India, which was hit by the worst drought in decades in 2016. All over the planet, growing populations and over-consumption are combining with shifting weather patterns and environmental impact to create a growing water crisis.
But as the saying goes, “necessity is the mother of invention”. And there’s nothing like an impending crisis to make people take stock of a problem and look for solutions!
Further Reading: NASA Earth Observatory
By popular request, Isaac Arthur and I have teamed up again to bring you a vision of the future of human space exploration. This time, we bring you practical construction tips from a pair of Type 2 Civilization engineers.
To make this collaboration even better, we’ve teamed up with two artists, Kevin Gill and Sergio Botero. They’re going to help create some special art, just for this episode, to help show what some of these megaprojects might look like.
Host: Fraser Cain (@fcain)
Their stories this week:
We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!
If you would like to sign up for the AstronomyCast Solar Eclipse Escape, where you can meet Fraser and Pamela, plus WSH Crew and other fans, visit our site linked above and sign up!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page<
Perhaps the most important question we can possible ask is, “are we alone in the Universe?”.
And so far, the answer has been, “I don’t know”. I mean, it’s a huge Universe, with hundreds of billions of stars in the Milky Way, and now we learn there are trillions of galaxies in the Universe.
Is there life closer to home? What about in the Solar System? There are a few existing places we could look for life close to home. Really any place in the Solar System where there’s liquid water. Wherever we find water on Earth, we find life, so it make sense to search for places with liquid water in the Solar System.
I know, I know, life could take all kinds of wonderful forms. Enlightened beings of pure energy, living among us right now. Or maybe space whales on Titan that swim through lakes of ammonia. Beep boop silicon robot lifeforms that calculate the wasted potential of our lives.
Sure, we could search for those things, and we will. Later. We haven’t even got this basic problem done yet. Earth water life? Check! Other water life? No idea.
It turns out, water’s everywhere in the Solar System. In comets and asteroids, on the icy moons of Jupiter and Saturn, especially Europa or Enceladus. Or you could look for life on Mars.
Mars is similar to Earth in many ways, however, it’s smaller, has less gravity, a thinner atmosphere. And unfortunately, it’s bone dry. There are vast polar caps of water ice, but they’re frozen solid. There appears to be briny liquid water underneath the surface, and it occasionally spurts out onto the surface. Because it’s close and relatively easy to explore, it’s been the place scientists have gone looking for past or current life.
Researchers tried to answer the question with NASA’s twin Viking Landers, which touched down in 1976. The landers were both equipped with three biology experiments. The researchers weren’t kidding around, they were going to nail this question: is there life on Mars?
In the first experiment, they took soil samples from Mars, mixed in a liquid solution with organic and inorganic compounds, and then measured what chemicals were released. In a second experiment, they put Earth organic compounds into Martian soil, and saw carbon dioxide released. In the third experiment, they heated Martian soil and saw organic material come out of the soil.
Three experiments, and stuff happened in all three. Stuff! Pretty exciting, right? Unfortunately, there were equally plausible non-biological explanations for each of the results. The astrobiology community wasn’t convinced, and they still fight in brutal cage matches to this day. It was ambitious, but inconclusive. The worst kind of conclusive.
Researchers found more inconclusive evidence in 1994. Ugh, there’s that word again. They were studying a meteorite that fell in Antarctica, but came from Mars, based on gas samples taken from inside the rock.
They thought they found evidence of fossilized bacterial life inside the meteorite. But again, there were too many explanations for how the life could have gotten in there from here on Earth. Life found a way… to burrow into a rock from Mars.
NASA learned a powerful lesson from this experience. If they were going to prove life on Mars, they had to go about it carefully and conclusively, building up evidence that had no controversy.
The Spirit and Opportunity Rovers were an example of building up this case cautiously. They were sent to Mars in 2004 to find evidence of water. Not water today, but water in the ancient past. Old water Over the course of several years of exploration, both rovers turned up multiple lines of evidence there was water on the surface of Mars in the ancient past.
They found concretions, tiny pebbles containing iron-rich hematite that forms on Earth in water. They found the mineral gypsum; again, something that’s deposited by water on Earth.
NASA’s Curiosity Rover took this analysis to the next level, arriving in 2012 and searching for evidence that water was on Mars for vast periods of time; long enough for Martian life to evolve.
Once again, Curiosity found multiple lines of evidence that water acted on the surface of Mars. It found an ancient streambed near its landing site, and drilled into rock that showed the region was habitable for long periods of time.
In 2014, NASA turned the focus of its rovers from looking for evidence of water to searching for past evidence of life.
Curiosity found one of the most interesting targets: a strange strange rock formations while it was passing through an ancient riverbed on Mars. While it was examining the Gillespie Lake outcrop in Yellowknife Bay, it photographed sedimentary rock that looks very similar to deposits we see here on Earth. They’re caused by the fossilized mats of bacteria colonies that lived billions of years ago.
Not life today, but life when Mars was warmer and wetter. Still, fossilized life on Mars is better than no life at all. But there might still be life on Mars, right now, today. The best evidence is not on its surface, but in its atmosphere. Several spacecraft have detected trace amounts of methane in the Martian atmosphere.
Methane is a chemical that breaks down quickly in sunlight. If you farted on Mars, the methane from your farts would dissipate in a few hundred years. If spacecraft have detected this methane in the atmosphere, that means there’s some source replenishing those sneaky squeakers. It could be volcanic activity, but it might also be life. There could be microbes hanging on, in the last few places with liquid water, producing methane as a byproduct.
The European ExoMars orbiter just arrived at Mars, and its main job is sniff the Martian atmosphere and get to the bottom of this question.
Are there trace elements mixed in with the methane that means its volcanic in origin? Or did life create it? And if there’s life, where is it located? ExoMars should help us target a location for future study.
NASA is following up Curiosity with a twin rover designed to search for life. The Mars 2020 Rover will be a mobile astrobiology laboratory, capable of scooping up material from the surface of Mars and digesting it, scientifically speaking. It’ll search for the chemicals and structures produced by past life on Mars. It’ll also collect samples for a future sample return mission.
Even if we do discover if there’s life on Mars, it’s entirely possible that we and Martian life are actually related by a common ancestor, that split off billions of years ago. In fact, some astrobiologists think that Mars is a better place for life to have gotten started.
Not the dry husk of a Red Planet that we know today, but a much wetter, warmer version that we now know existed billions of years ago. When the surface of Mars was warm enough for liquid water to form oceans, lakes and rivers. And we now know it was like this for millions of years.
While Earth was still reeling from an early impact by the massive planet that crashed into it, forming the Moon, life on Mars could have gotten started early.
But how could we actually be related? The idea of Panspermia says that life could travel naturally from world to world in the Solar System, purely through the asteroid strikes that were regularly pounding everything in the early days.
Imagine an asteroid smashing into a world like Mars. In the lower gravity of Mars, debris from the impact could be launched into an escape trajectory, free to travel through the Solar System.
We know that bacteria can survive almost indefinitely, freeze dried, and protected from radiation within chunks of space rock. So it’s possible they could make the journey from Mars to Earth, crossing the orbit of our planet.
Even more amazingly, the meteorites that enter the Earth’s atmosphere would protect some of the bacterial inhabitants inside. As the Earth’s atmosphere is thick enough to slow down the descent of the space rocks, the tiny bacterialnauts could survive the entire journey from Mars, through space, to Earth.
If we do find life on Mars, how will we know it’s actually related to us? If Martian life has the similar DNA structure to Earth life, it’s probably related. In fact, we could probably trace the life back to determine the common ancestor, and even figure out when the tiny lifeforms make the journey.
If we do find life on Mars, which is related to us, that just means that life got around the Solar System. It doesn’t help us answer the bigger question about whether there’s life in the larger Universe. In fact, until we actually get a probe out to nearby stars, or receive signals from them, we might never know.
An even more amazing possibility is that it’s not related. That life on Mars arose completely independently. One clue that scientists will be looking for is the way the Martian life’s instructions are encoded. Here on Earth, all life follows “left-handed chirality” for the amino acid building blocks that make up DNA and RNA. But if right-handed amino acids are being used by Martian life, that would mean a completely independent origin of life.
Of course, if the life doesn’t use amino acids or DNA at all, then all bets are off. It’ll be truly alien, using a chemistry that we don’t understand at all.
There are many who believe that Mars isn’t the best place in the Solar System to search for life, that there are other places, like Europa or Enceladus, where there’s a vast amount of liquid water to be explored.
But Mars is close, it’s got a surface you can land on. We know there’s liquid water beneath the surface, and there was water there for a long time in the past. We’ve got the rovers, orbiters and landers on the planet and in the works to get to the bottom of this question. It’s an exciting time to be part of this search.
Science fiction has told us again and again, we belong out there, among the stars. But before we can build that vast galactic empire, we’ve got to learn how to just survive in space. Fortunately, we happen to live in a Solar System with many worlds, large and small that we can use to become a spacefaring civilization.
This is half of an epic two-part article that I’m doing with Isaac Arthur, who runs an amazing YouTube channel all about futurism, often about the exploration and colonization of space. Make sure you subscribe to his channel.
This article is about colonizing the inner Solar System, from tiny Mercury, the smallest planet, out to Mars, the focus of so much attention by Elon Musk and SpaceX. In the other article, Isaac will talk about what it’ll take to colonize the outer Solar System, and harness its icy riches. You can read these articles in either order, just read them both.
At the time I’m writing this, humanity’s colonization efforts of the Solar System are purely on Earth. We’ve exploited every part of the planet, from the South Pole to the North, from huge continents to the smallest islands. There are few places we haven’t fully colonized yet, and we’ll get to that.
But when it comes to space, we’ve only taken the shortest, most tentative steps. There have been a few temporarily inhabited space stations, like Mir, Skylab and the Chinese Tiangong Stations.
Our first and only true colonization of space is the International Space Station, built in collaboration with NASA, ESA, the Russian Space Agency and other countries. It has been permanently inhabited since November 2nd, 2000. Needless to say, we’ve got our work cut out for us.
Before we talk about the places and ways humans could colonize the rest of the Solar System, it’s important to talk about what it takes to get from place to place.
Just to get from the surface of Earth into orbit around our planet, you need to be going about 10 km/s sideways. This is orbit, and the only way we can do it today is with rockets. Once you’ve gotten into Low Earth Orbit, or LEO, you can use more propellant to get to other worlds.
If you want to travel to Mars, you’ll need an additional 3.6 km/s in velocity to escape Earth gravity and travel to the Red Planet. If you want to go to Mercury, you’ll need another 5.5 km/s.
And if you wanted to escape the Solar System entirely, you’d need another 8.8 km/s. We’re always going to want a bigger rocket.
The most efficient way to transfer from world to world is via the Hohmann Transfer. This is where you raise your orbit and drift out until you cross paths with your destination. Then you need to slow down, somehow, to go into orbit.
One of our primary goals of exploring and colonizing the Solar System will be to gather together the resources that will make future colonization and travel easier. We need water for drinking, and to split it apart for oxygen to breathe. We can also turn this water into rocket fuel. Unfortunately, in the inner Solar System, water is a tough resource to get and will be highly valued.
We need solid ground. To build our bases, to mine our resources, to grow our food, and to protect us from the dangers of space radiation. The more gravity we can get the better, since low gravity softens our bones, weakens our muscles, and harms us in ways we don’t fully understand.
Each world and place we colonize will have advantages and disadvantages. Let’s be honest, Earth is the best place in the Solar System, it’s got everything we could ever want and need. Everywhere else is going to be brutally difficult to colonize and make self-sustaining.
We do have one huge advantage, though. Earth is still here, we can return whenever we like. The discoveries made on our home planet will continue to be useful to humanity in space through communications, and even 3D printing. Once manufacturing is sophisticated enough, a discovery made on one world could be mass produced half a solar system away with the right raw ingredients.
We will learn how to make what we need, wherever we are, and how to transport it from place to place, just like we’ve always done.
Mercury is the closest planet from the Sun, and one of the most difficult places that we might attempt the colonize. Because it’s so close to the Sun, it receives an enormous amount of energy. During the day, temperatures can reach 427 C, but without an atmosphere to trap the heat, night time temperatures dip down to -173 C. There’s essentially no atmosphere, 38% the gravity of Earth, and a single solar day on Mercury lasts 176 Earth days.
Mercury does have some advantages, though. It has an average density almost as high as Earth, but because of its smaller size, it actually means it has a higher percentage of metal than Earth. Mercury will be incredibly rich in metals and minerals that future colonists will need across the Solar System.
With the lower gravity and no atmosphere, it’ll be far easier to get that material up into orbit and into transfer trajectories to other worlds.
But with the punishing conditions on the planet, how can we live there? Although the surface of Mercury is either scorching or freezing, NASA’s MESSENGER spacecraft turned up regions of the planet which are in eternal shadow near the poles. In fact, these areas seem to have water ice, which is amazing for anywhere this close to the Sun.
You could imagine future habitats huddled into those craters, pulling in solar power from just over the crater rim, using the reservoirs of water ice for air, fuel and water.
High powered solar robots could scour the surface of Mercury, gathering rare metals and other minerals to be sent off world. Because it’s bathed in the solar winds, Mercury will have large deposits of Helium-3, useful for future fusion reactors.
Over time, more and more of the raw materials of Mercury will find their way to the resource hungry colonies spread across the Solar System.
It also appears there are lava tubes scattered across Mercury, hollows carved out by lava flows millions of years ago. With work, these could be turned into safe, underground habitats, protected from the radiation, high temperatures and hard vacuum on the surface.
With enough engineering ability, future colonists will be able to create habitats on the surface, wherever they like, using a mushroom-shaped heat shield to protect a colony built on stilts to keep it off the sun-baked surface.
Mercury is smaller than Mars, but is a good deal denser, so it has about the same gravity, 38% of Earth’s. Now that might turn out to be just fine, but if we need more, we have the option of using centrifugal force to increase it. Space Stations can generate artificial gravity by spinning, but you can combine normal gravity with spin-gravity to create a stronger field than either would have.
So our mushroom habitat’s stalk could have an interior spinning section with higher gravity for those living inside it. You get a big mirror over it, shielding you from solar radiation and heat, you have stilts holding it off the ground, like roots, that minimize heat transfer from the warmer areas of ground outside the shield, and if you need it you have got a spinning section inside the stalk. A mushroom habitat.
Venus is the second planet in the Solar System, and it’s the evil twin of Earth. Even though it has roughly the same size, mass and surface gravity of our planet, it’s way too close to the Sun. The thick atmosphere acts like a blanket, trapping the intense heat, pushing temperatures at the surface to 462 C.
Everywhere on the planet is 462 C, so there’s no place to go that’s cooler. The pure carbon dioxide atmosphere is 90 times thicker than Earth, which is equivalent to being a kilometer beneath the ocean on Earth.
In the beginning, colonizing the surface of Venus defies our ability. How do you survive and stay cool in a thick poisonous atmosphere, hot enough to melt lead? You get above it.
One of the most amazing qualities of Venus is that if you get into the high atmosphere, about 52.5 kilometers up, the air pressure and temperature are similar to Earth. Assuming you can get above the poisonous clouds of sulphuric acid, you could walk outside a floating colony in regular clothes, without a pressure suit. You’d need a source of breathable air, though.
Even better, breathable air is a lifting gas in the cloud tops of Venus. You could imagine a future colony, filled with breathable air, floating around Venus. Because the gravity on Venus is roughly the same as Earth, humans wouldn’t suffer any of the side effects of microgravity. In fact, it might be the only place in the entire Solar System other than Earth where we don’t need to account for low gravity.
Now the day on Venus is incredibly long, 243 earth days, so if you stay over the same place the whole time it would be light for four months then dark for four months. Not ideal for solar power on a first glance, but Venus turns so slowly that even at the equator you could stay ahead of the sunset at a fast walk.
So if you have floating colonies it would take very little effort to stay constantly on the light side or dark side or near the twilight zone of the terminator. You are essentially living inside a blimp, so it may as well be mobile. And on the day side it would only take a few solar panels and some propellers to stay ahead. And since it is so close to the Sun, there’s plenty of solar power. What could you do with it?
The atmosphere itself would probably serve as a source of raw materials. Carbon is the basis for all life on Earth. We’ll need it for food and building materials in space. Floating factories could process the thick atmosphere of Venus, to extract carbon, oxygen, and other elements.
Heat resistant robots could be lowered down to the surface to gather minerals and then retrieved before they’re cooked to death.
Venus does have a high gravity, so launching rockets up into space back out of Venus’ gravity well will be expensive.
Over longer periods of time, future colonists might construct large solar shades to shield themselves from the scorching heat, and eventually, even start cooling the planet itself.
The next planet from the Sun is Earth, the best planet in the Solar System. One of the biggest advantages of our colonization efforts will be to get heavy industry off our planet and into space. Why pollute our atmosphere and rivers when there’s so much more space… in space.
Over time, more and more of the resource gathering will happen off world, with orbital power generation, asteroid mining, and zero gravity manufacturing. Earth’s huge gravity well means that it’s best to bring materials down to Earth, not carry them up to space.
However, the normal gravity, atmosphere and established industry of Earth will allow us to manufacture the lighter high tech goods that the rest of the Solar System will need for their own colonization efforts.
But we haven’t completely colonized Earth itself. Although we’ve spread across the land, we know very little about the deep ocean. Future colonies under the oceans will help us learn more about self-sufficient colonies, in extreme environments. The oceans on Earth will be similar to the oceans on Europa or Enceladus, and the lessons we learn here will teach us to live out there.
As we return to space, we’ll colonize the region around our planet. We’ll construct bigger orbital colonies in Low Earth Orbit, building on our lessons from the International Space Station.
One of the biggest steps we need to take, is understanding how to overcome the debilitating effects of microgravity: the softened bones, weakened muscles and more. We need to perfect techniques for generating artificial gravity where there is none.
The best technique we have is rotating spacecraft to generate artificial gravity. Just like we saw in 2001, and The Martian, by rotating all or a portion of a spacecraft, you can generated an outward centrifugal force that mimics the acceleration of gravity. The larger the radius of the space station, the more comfortable and natural the rotation feels.
Low Earth Orbit also keeps a space station within the Earth’s protective magnetosphere, limiting the amount of harmful radiation that future space colonists will experience.
Other orbits are useful too, including geostationary orbit, which is about 36,000 kilometers above the surface of the Earth. Here spacecraft orbit the Earth at exactly the same rate as the rotation of Earth, which means that stations appear in fixed positions above our planet, useful for communication.
Geostationary orbit is higher up in Earth’s gravity well, which means these stations will serve a low-velocity jumping off points to reach other places in the Solar System. They’re also outside the Earth’s atmospheric drag, and don’t require any orbital boosting to keep them in place.
By perfecting orbital colonies around Earth, we’ll develop technologies for surviving in deep space, anywhere in the Solar System. The same general technology will work anywhere, whether we’re in orbit around the Moon, or out past Pluto.
When the technology is advanced enough, we might learn to build space elevators to carry material and up down from Earth’s gravity well. We could also build launch loops, electromagnetic railguns that launch material into space. These launch systems would also be able to loft supplies into transfer trajectories from world to world throughout the Solar System.
Earth orbit, close to the homeworld gives us the perfect place to develop and perfect the technologies we need to become a true spacefaring civilization. Not only that, but we’ve got the Moon.
The Moon, of course, is the Earth’s only natural satellite, which orbits us at an average distance of about 400,000 kilometers. Almost ten times further than geostationary orbit.
The Moon takes a surprising amount of velocity to reach from Low Earth Orbit. It’s close, but expensive to reach, thrust speaking.
But that fact that it’s close makes the Moon an ideal place to colonize. It’s close to Earth, but it’s not Earth. It’s airless, bathed in harmful radiation and has very low gravity. It’s the place that humanity will learn to survive in the harsh environment of space.
But it still does have some resources we can exploit. The lunar regolith, the pulverized rocky surface of the Moon, can be used as concrete to make structures. Spacecraft have identified large deposits of water at the Moon’s poles, in its permanently shadowed craters. As with Mercury, these would make ideal locations for colonies.
Our spacecraft have also captured images of openings to underground lava tubes on the surface of the Moon. Some of these could be gigantic, even kilometers high. You could fit massive cities inside some of these lava tubes, with room to spare.
Helium-3 from the Sun rains down on the surface of the Moon, deposited by the Sun’s solar wind, which could be mined from the surface and provide a source of fuel for lunar fusion reactors. This abundance of helium could be exported to other places in the Solar System.
The far side of the Moon is permanently shadowed from Earth-based radio signals, and would make an ideal location for a giant radio observatory. Telescopes of massive size could be built in the much lower lunar gravity.
We talked briefly about an Earth-based space elevator, but an elevator on the Moon makes even more sense. With the lower gravity, you can lift material off the surface and into lunar orbit using cables made of materials we can manufacture today, such as Zylon or Kevlar.
One of the greatest threats on the Moon is the dusty regolith itself. Without any kind of weathering on the surface, these dust particles are razor sharp, and they get into everything. Lunar colonists will need very strict protocols to keep the lunar dust out of their machinery, and especially out of their lungs and eyes, otherwise it could cause permanent damage.
Although the vast majority of asteroids in the Solar System are located in the main asteroid belt, there are still many asteroids orbiting closer to Earth. These are known as the Near Earth Asteroids, and they’ve been the cause of many of Earth’s great extinction events.
These asteroids are dangerous to our planet, but they’re also an incredible resource, located close to our homeworld.
The amount of velocity it takes to get to some of these asteroids is very low, which means travel to and from these asteroids takes little energy. Their low gravity means that extracting resources from their surface won’t take a tremendous amount of energy.
And once the orbits of these asteroids are fully understood, future colonists will be able to change the orbits using thrusters. In fact, the same system they use to launch minerals off the surface would also push the asteroids into safer orbits.
These asteroids could be hollowed out, and set rotating to provide artificial gravity. Then they could be slowly moved into safe, useful orbits, to act as space stations, resupply points, and permanent colonies.
There are also gravitationally stable points at the Sun-Earth L4 and L5 Lagrange Points. These asteroid colonies could be parked there, giving us more locations to live in the Solar System.
The future of humanity will include the colonization of Mars, the fourth planet from the Sun. On the surface, Mars has a lot going for it. A day on Mars is only a little longer than a day on Earth. It receives sunlight, unfiltered through the thin Martian atmosphere. There are deposits of water ice at the poles, and under the surface across the planet.
Martian ice will be precious, harvested from the planet and used for breathable air, rocket fuel and water for the colonists to drink and grow their food. The Martian regolith can be used to grow food. It does have have toxic perchlorates in it, but that can just be washed out.
The lower gravity on Mars makes it another ideal place for a space elevator, ferrying goods up and down from the surface of the planet.
Unlike the Moon, Mars has a weathered surface. Although the planet’s red dust will get everywhere, it won’t be toxic and dangerous as it is on the Moon.
Like the Moon, Mars has lava tubes, and these could be used as pre-dug colony sites, where human Martians can live underground, protected from the hostile environment.
Mars has two big problems that must be overcome. First, the gravity on Mars is only a third that of Earth’s, and we don’t know the long term impact of this on the human body. It might be that humans just can’t mature properly in the womb in low gravity.
Researchers have proposed that Mars colonists might need to spend large parts of their day on rotating centrifuges, to simulate Earth gravity. Or maybe humans will only be allowed to spend a few years on the surface of Mars before they have to return to a high gravity environment.
The second big challenge is the radiation from the Sun and interstellar cosmic rays. Without a protective magnetosphere, Martian colonists will be vulnerable to a much higher dose of radiation. But then, this is the same challenge that colonists will face anywhere in the entire Solar System.
That radiation will cause an increased risk of cancer, and could cause mental health issues, with dementia-like symptoms. The best solution for dealing with radiation is to block it with rock, soil or water. And Martian colonists, like all Solar System colonists will need to spend much of their lives underground or in tunnels carved out of rock.
In addition to Mars itself, the Red Planet has two small moons, Phobos and Deimos. These will serve as ideal places for small colonies. They’ll have the same low gravity as asteroid colonies, but they’ll be just above the gravity well of Mars. Ferries will travel to and from the Martian moons, delivering fresh supplies and sending Martian goods out to the rest of the Solar System.
We’re not certain yet, but there are good indicators these moons might have ice inside them, if so that is an excellent source of fuel and could make initial trips to Mars much easier by allowing us to send a first expedition to those moons, who then begin producing fuel to be used to land on Mars and to leave Mars and return home.
According to Elon Musk, if a Martian colony can reach a million inhabitants, it’ll be self-sufficient from Earth or any other world. At that point, we would have a true, Solar System civilization.
Now, continue on to the other half of this article, written by Isaac Arthur, where he talks about what it will take to colonize the outer Solar System. Where water ice is plentiful but solar power is feeble. Where travel times and energy require new technologies and techniques to survive and thrive.
Water has been showing up in all sorts of unexpected places in our Solar System, such as the Moon, Mercury and Jupiter’s moon Ganymede. Add one more place to the list: Asteroid 16 Psyche. This metal-rich asteroid may have traces of water molecules on its surface that shouldn’t be there, researchers say.
Psyche is thought to be the largest metallic asteroid in the Solar System, at 300 km (186 miles) across and likely consists of almost pure nickel-iron metal. Scientists had thought Psyche was made up of the leftover core of a protoplanet that was mostly destroyed by impacts billions of years ago, but they may now be rethinking that.
“The detection of a 3 micron hydration absorption band on Psyche suggests that this asteroid may not be metallic core, or it could be a metallic core that has been impacted by carbonaceous material over the past 4.5 Gyr,” the team said in their paper.
While previous observations of Psyche had shown no evidence for water on its surface, new observations with the NASA Infrared Telescope Facility found evidence for volatiles such as water or hydroxyl on the asteroid’s surface. Hydroxyl is a free radical consisting of one hydrogen atom bound to one oxygen atom.
“We did not expect a metallic asteroid like Psyche to be covered by water and/or hydroxyl,” said Vishnu Reddy, from the University of Arizona’s Lunar and Planetary Laboratory, a co-author of the new paper about Psyche. “Metal-rich asteroids like Psyche are thought to have formed under dry conditions without the presence of water or hydroxyl, so we were puzzled by our observations at first.”
Asteroids usually fall into two categories: those rich in silicates, and those rich in carbon and volatiles. Metallic asteroids like Psyche are extremely rare, making it a laboratory to study how planets formed.
For now, the source of the water on Psyche remains a mystery. But Redddy and his colleagues propose a few different explanations. One is, again, Psyche may not be as metallic as previously thought. Another option is that the water or hydroxyl could be the product of solar wind interacting with silicate minerals on Psyche’s surface, such as what is occurring on the Moon.
The most likely explanation, however is that the water seen on Psyche might have been delivered by carbonaceous asteroids that impacted Psyche in the distant past, as is thought to have occurred on early Earth.
“Our discovery of carbon and water on an asteroid that isn’t supposed to have those compounds supports the notion that these building blocks of life could have been delivered to our Earth early in the history of our solar system,” said Reddy.
If we’re lucky, we won’t have to wait too long to find out more about Psyche. A mission to Psyche is on the short list of mission proposals being considered by NASA, with a potential launch as early as 2020. Reddy and team said an orbiting spacecraft could explore this unique asteroid and determine if whether there is water or hydroxyl on the surface.
An isolated 3-mile-high (5 km) mountain Ahuna Mons on Ceres is likely volcanic in origin, and the dwarf planet may have a weak, temporary atmosphere. These are just two of many new insights about Ceres from NASA’s Dawn mission published this week in six papers in the journal Science.
“Dawn has revealed that Ceres is a diverse world that clearly had geological activity in its recent past,” said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles.
Ahuna Mons is a volcanic dome similar to earthly and lunar volcanic domes but unique in the solar system, according to a new analysis led by Ottaviano Ruesch of NASA’s Goddard Space Flight Center and the Universities Space Research Association. While those on Earth erupt with molten rock, Ceres’ grandest peak likely formed as a salty-mud volcano. Instead of molten rock, salty-mud volcanoes, or “cryovolcanoes,” release frigid, salty water sometimes mixed with mud.
Learn more about Ahuna Mons
“This is the only known example of a cryovolcano that potentially formed from a salty mud mix, and that formed in the geologically recent past,” Ruesch said. Estimates place the mountain formation within the past billion years.
Dawn may also have detected a weak, temporary atmosphere; the probe’s gamma ray and neutron (GRaND) detector observed evidence that Ceres had accelerated electrons from the solar wind to very high energies over a period of about six days. In theory, the interaction between the solar wind’s energetic particles and atmospheric molecules could explain the GRaND observations.
A temporary atmosphere would confirm the water vapor the Herschel Space Observatory detected at Ceres in 2012-2013. The electrons that GRaND detected could have been produced by the solar wind hitting the water molecules that Herschel observed, but scientists are also looking into alternative explanations.
While Ahuna Mons may have erupted liquid water in the not-too-distant past, Dawn found probable water ice right now in the mid-latitude Oxo Crater using its visible and infrared mapping spectrometer (VIR).
Exposed water-ice is rare on the dwarf planet, but the low density of Ceres — 2.08 grams/cm3 vs. 5.5 for Earth — the impact-generated ice detection and the the existence of Ahuna Mons suggest that Ceres’ crust does contain a significant amount of water ice.
Impact craters are clearly the most abundant geological feature on Ceres, and their different shapes help tell the complex story of Ceres’ past. Craters that are roughly polygonal — shapes bounded by straight lines — hint that Ceres’ crust is heavily fractured. In addition, several Cerean craters display fractures on their floors. There are craters with flow-like features. Bright areas are peppered across Ceres, with the most reflective ones in Occator Crater. Some crater shapes could indicate water-ice in the subsurface.
All these crater forms imply an outer shell for Ceres that is not purely ice or rock, but rather a mixture of both. Scientists also calculated the ratio of various craters’ depths to diameters, and found that some amount of crater relaxation must have occurred as icy walls gradually slump.
“The uneven distribution of craters indicates that the crust is not uniform, and that Ceres has gone through a complex geological evolution,” Hiesinger said.
Ceres’ crust also appears loaded with clay-forming minerals called phyllosilicates. These phyllosilicates are rich in magnesium and also have some ammonium embedded in their crystalline structure. Their distribution throughout the dwarf planet’s crust indicates Ceres’ surface material has been altered by a global process involving water.
Now in its extended mission, the Dawn spacecraft has been increasing its altitude since Sept. 2 as scientists stand back once again for a broader look at Ceres under different lighting conditions now compared to earlier in the mission.
Brown dwarfs – those not-quite-a-planet and not-quite-a-star objects – are intriguing oddities that are too low in mass to burn hydrogen, but are more massive than planets. They only emit a faint amount of light, so they are hard to detect, making scientists unsure of how many of them might be out there in our galaxy.
But astronomers have been keeping an eye one particular brown dwarf known called WISE 0855. Just 7.2 light-years from Earth, it is the coldest known object outside of our Solar System and is just barely visible at infrared wavelengths. But with some crafty spectroscopic observing techniques, astronomers have now determined this object has some exciting characteristics: its atmosphere is full of clouds of water vapor. This is the first time water clouds have been detected outside of our Solar System.
“It’s five times fainter than any other object detected with ground-based spectroscopy at this wavelength,” said Andrew Skemer, assistant professor of astronomy and astrophysics at UC Santa Cruz and the first author on a paper on WISE 0855 published in Astrophysical Journal Letters (paper is available on arXiv here). “Now that we have a spectrum, we can really start thinking about what’s going on in this object. Our spectrum shows that WISE 0855 is dominated by water vapor and clouds, with an overall appearance that is strikingly similar to Jupiter.”
This brown dwarf’s full name is WISE J085510.83-071442.5, but we’re among friends, so it’s W0855 for short. It has about five times the mass of Jupiter and is the coldest brown dwarf ever detected, with an average temperature of about 250 degrees Kelvin, or minus 10 degrees F, minus 20 C. That makes it nearly as cold as Jupiter, which is 130 degrees Kelvin.
“WISE 0855 is our first opportunity to study an extrasolar planetary-mass object that is nearly as cold as our own gas giants,” Skemer said.
Skemer and his team used the Gemini-North telescope in Hawaii and the Gemini Near Infrared Spectrograph to observe WISE 0855 over 13 nights for a total of about 14 hours. Skemer was part of a team that studied this object in 2014 found tentative indications of water clouds based on very limited photometric data. Skemer said obtaining a spectrum (which separates the light from an object into its component wavelengths) was the only way to detect this object’s molecular composition.
A video about the 2014 discovery and study of WISE 0855:
WISE 0855 is too faint for conventional spectroscopy at optical or near-infrared wavelengths, but the team took up a challenge and looked at the thermal emissions from the object at wavelengths in a narrow window around 5 microns.
“I think everyone on the research team really believed that we were dreaming to think we could obtain a spectrum of this brown dwarf because its thermal glow is so feeble,” said Skemer. WISE 0855, is so cool and faint that many astronomers thought it would be years before a spectrum could be obtained. “I thought we’d have to wait until the James Webb Space Telescope was operating to do this,” Skemer said.
This spectroscopic view provided a glimpse into the environment of WISE 0855’s atmosphere. With the data in hand, the researchers then developed atmospheric models of the equilibrium chemistry for a brown dwarf at 250 degrees Kelvin and calculated the resulting spectra under different assumptions, including cloudy and cloud-free models. The models predicted a spectrum dominated by features resulting from water vapor, and the cloudy model yielded the best fit to the features in the spectrum of WISE 0855.
While the spectra of this object are strikingly similar to Jupiter, WISE 0855 appears to have a less turbulent atmosphere.
“The spectrum allows us to investigate dynamical and chemical properties that have long been studied in Jupiter’s atmosphere, but this time on an extrasolar world,” Skemer said.
The scientists say WISE 0855 looks more similar to Jupiter than any exoplanet yet discovered, which is especially intriguing since the Juno mission has just begun its exploration at the giant world. Jupiter, along with the other gas planets in our Solar System, all have clouds and storms, although Jupiter’s clouds are mainly made of ammonia with lower level clouds perhaps containing water. One of Juno’s goals is to determine the global water abundance at Jupiter.
A crowning achievement of the Cassini mission to Saturn is the discovery of water vapor jets spraying out from Enceladus‘ southern pole. First witnessed by the spacecraft in 2005, these icy geysers propelled the little 515-kilometer-wide moon into the scientific spotlight and literally rewrote the mission’s objectives. After 22 flybys of Enceladus during its nearly twelve years in orbit around Saturn, Cassini has gathered enough data to determine that there is a global subsurface ocean of salty liquid water beneath Enceladus’ frozen crust—an ocean that gets sprayed into space from long “tiger stripe” fissures running across the moon’s southern pole. Now, new research has shown that at least some of the vapor jets get a boost in activity when Enceladus is farther from Saturn.
By measuring the changes in brightness of a distant background star as Enceladus’ plumes passed in front of it in March 2016, Cassini observed a significant increase in the amount of icy particles being ejected by one particular jet source.
Named “Baghdad 1,” the jet went from contributing 2% of the total vapor content of the entire plume area to 8% when Enceladus was at the farthest point in its slightly-eccentric orbit around Saturn. This small yet significant discovery indicates that, although Enceladus’ plumes are reacting to morphological changes to the moon’s crust due to tidal flexing, it’s select small-scale jets that are exhibiting the most variation in output (rather than a simple, general increase in outgassing across the full plumes.)
“How do the tiger stripe fissures respond to the push and pull of tidal forces as Enceladus goes around its orbit to explain this difference? We now have new clues!” said Candice Hansen, senior scientist at the Planetary Science Institute and lead planner of the study. “It may be that the individual jet sources along the tiger stripes have a particular shape or width that responds most strongly to the tidal forcing each orbit to boost more ice grains at this orbital longitude.”
The confirmation that Enceladus shows an increase in overall plume output at farther points from Saturn was first made in 2013.
Whether this new finding means that the internal structure of the fissures is different than what scientists have suspected or some other process is at work either within Enceladus or in its orbit around Saturn still remains to be determined.
“Since we can only see what’s going on above the surface, at the end of the day, it’s up to the modelers to take this data and figure out what’s going on underground,” said Hansen.