Artist's depiction of a waterworld. A new study suggests that Earth is in a minority when it comes to planets, and that most habitable planets may be greater than 90% ocean. Credit: David A. Aguilar (CfA)
Evidence from an ancient section of the Earth’s crust suggest that Earth was once a water-world, some three billion years ago. If true, it’ll mean scientists need to reconsider some thinking around exoplanets and habitability. They’ll also need to reconsider their understanding of how life began on our planet.
The fascinating surface of Jupiter’s icy moon Europa looms large in this newly-reprocessed color view, made from images taken by NASA's Galileo spacecraft in the late 1990s. This is the color view of Europa from Galileo that shows the largest portion of the moon's surface at the highest resolution. Credits: NASA/JPL-Caltech/SETI Institute
What’s been long-suspected has now been confirmed: Jupiter’s moon Europa has water. As we’ve learned more about the outer Solar System in recent years, Europa has become a high-priority target in the search for life. With this discovery, NASA has just painted a big red bulls-eye on Jupiter’s smallest Galilean moon.
An artist's concept of K2-18b, a super-Earth exoplanet that could support life. But, not all habitable planets are pale blue dots. Some are dry and yellow. Courtesy STScI
Astronomers using the Hubble space telescope have discovered water in the atmosphere of an exoplanet in its star’s habitable zone. If confirmed, it will be the first time we’ve detected water—a critical ingredient for life as we know it—on an exoplanet. The water was detected as vapour in the atmosphere, but the temperature of the planet means it could sustain liquid water on its surface, if it’s rocky.
Detailed view of the rubble-pile asteroid 25143 Itokawa visited by the Japanese spacecraft Hayabusa in 2005. Credit: JAXA
Right now, the Japanese Aerospace Exploration Agency‘s (JAXA) Hayabusa2 spacecraft is busy exploring the asteroid 162173 Ryugu. Like it’s predecessor, this consists of a sample-return mission, where regolith from the asteroid’s surface will be brought back home for analysis. In addition to telling us more about the early Solar System, these studies are expected to shed light on the origin of Earth’s water (and maybe even life).
Meanwhile, scientists here at home have been busy examining the samples returned from 25143 Itokawa by the Hayabusa1spacecraft. Thanks to a recent study by a pair of cosmochemists from Arizona State University (ASU), it is now known that this asteroid contained abundant amounts of water. From this, the team estimates that up to half the water on Earth could have come from asteroid and comet impacts billions of years ago.
A topographic image of an area of anceint riverbeds on Mars. Created with data from the High-Resolution Stereo Camera on the Mars Express Orbiter. Image Credit: ESA/DLR/FU Berlin http://www.esa.int/spaceinimages/ESA_Multimedia/Copyright_Notice_Images
Billions of years ago, Mars was likely a much warmer and wetter place than the cold, dry, barren world we see today. Whether there was life there or not remains an open question. But there’s a massive, growing wall of evidence showing that Mars may have had the necessary conditions for life in the past, including at least one system of river valley networks.
This view of Earth’s horizon was taken by an Expedition 7 crewmember onboard the International Space Station, using a wide-angle lens while the Station was over the Pacific Ocean. A new study suggests that Earth's water didn't all come from comets, but likely also came from water-rich planetesimals. Credit: NASA
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.
Animation showing the disappearance of Cape Town's water supply. Credit: NASA
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.
Theewaterskloof Dam—the largest reservoir and the source of roughly half of the city’s water. Credit: NASA
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.
Landsat image of the Theewaterskloof reservoir in October 10, 2017, when it was at 27 percent capacity. Credit: NASA
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.
Images showing three successive dry years and the toll they took on Cape Town’s water system. Credit: NASA
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.
Water level data water level data provided by South Africa’s Department of Water and Sanitation. Credit: NASA/DWS
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!
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.
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!
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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.
Sloping buttes and layered outcrops within the “Murray formation” layer of lower Mount Sharp. Credit: NASA
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.
The landing site of Viking 1 on Mars in 1977, with trenches dug in the soil for the biology experiments. Credit: NASA/JPL
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.
Artist Concept, Mars Exploration Rovers. NASA/JPL-Caltech
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.
A bright mineral vein informally named Homestake. The vein is about the width of a thumb and about 18 inches (45 centimeters) long. Opportunity examined it in November 2011 (Sol 2763) and found it to be rich in calcium and sulfur, possibly the calcium-sulfate mineral gypsum. Credit: NASA/JPL-Caltech
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.
A bright and interestingly shaped tiny pebble shows up among the soil on a rock, called “Gillespie Lake,” which was imaged by Curiosity’s Mars Hand Lens Imager on Dec. 19, 2012, the 132nd sol, or Martian day of Curiosity’s mission on Mars. Credit: NASA / JPL-Caltech / MSSS.
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.
The European/Russian ExoMars Trace Gas Orbiter (TGO) will sniff the Martian atmosphere for signs of methane which could originate for either biological or geological mechanisms. Credit: ESA
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.
A conception of an ancient Mars, flush with oceans, clouds and life. Credit: Kevin Gill.
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.
Credit: NASA/JPL-Caltech
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.
