Surface features of the four members at different levels of zoom in each row
Continuing with our “Definitive Guide to Terraforming“, Universe Today is happy to present to our guide to terraforming Jupiter’s Moons. Much like terraforming the inner Solar System, it might be feasible someday. But should we?
Fans of Arthur C. Clarke may recall how in his novel, 2010: Odyssey Two (or the movie adaptation called 2010: The Year We Make Contact), an alien species turned Jupiter into a new star. In so doing, Jupiter’s moon Europa was permanently terraformed, as its icy surface melted, an atmosphere formed, and all the life living in the moon’s oceans began to emerge and thrive on the surface.
As we explained in a previous video (“Could Jupiter Become a Star“) turning Jupiter into a star is not exactly doable (not yet, anyway). However, there are several proposals on how we could go about transforming some of Jupiter’s moons in order to make them habitable by human beings. In short, it is possible that humans could terraform one of more of the Jovians to make it suitable for full-scale human settlement someday.
We always see the same side of the Moon. It’s always up there, staring down at us with its terrifying visage. Or maybe it’s a creepy rabbit? Anyway, it’s always showing us the same face, and never any other part.
This is because the Moon is tidally locked to the Earth; the same fate that affects every single large moon orbiting a planet. The Moon is locked to the Earth, the Jovian moons are locked to Jupiter, Titan is locked to Saturn, etc.
As the Moon orbits the Earth, it slowly rotates to keep the same hemisphere facing us. Its day is as long as its year. And standing on the surface of the Moon, you’d see the Earth in roughly the same spot in the sky. Forever and ever.
Because of tidal locking, you’d see Earth in roughly the same spot from the Moon forever. For-eh-ver. For-EH-VER. Credit: NASA / Goddard / Arizona State University
We see this all across the Solar System.
But there’s one place where this tidal locking goes to the next level: the dwarf planet Pluto and its large moon Charon are tidally locked to each other. In other words, the same hemisphere of Pluto always faces Charon and vice versa.
It take Pluto about 6 and a half days for the Sun to return to the same point in the sky, which is the same time it takes Charon to complete an orbit, which is the same time it takes the Sun to pass through the sky on Charon.
Since Pluto eventually locked to its moon, can the same thing happen here on Earth. Will we eventually lock with the Moon?
Before we answer this question, let’s explain what’s going on here. Although the Earth and the Moon are spheres, they actually have a little variation. The gravity pulling on each world creates love handle tidal bulges on each world.
And these bulges act like a brake, slowing down the rotation of the world. Because the Earth has 81 times the mass of the Moon, it was the dominant force in this interaction.
In the early Solar System, both the Earth and the Moon rotated independently. But the Earth’s gravity grabbed onto those love handles and slowed down the rotation of the Moon. To compensate for the loss of momentum in the system, the Moon drifted away from the Earth to its current position, about 370,000 kilometers away.
But Moon has the same impact on the Earth. The same tidal forces that cause the tides on Earth are slowing down the Earth’s rotation bit by bit. And the Moon is continuing to drift away a few centimeters a year to compensate.
It’s hard to estimate exactly when, but over the course of tens of billions of years, the Earth will become locked to the Moon, just like Pluto and Charon.
Pluto and Charon are tidally locked to each other. Credit: NASA / JHUAPL / SwRI
Of course, this will be long after the Sun has died as a red giant. And there’s no way to know what kind of mayhem that’ll cause to the Earth-Moon system. Other planets in the Solar System may shift around, and maybe even eject the Earth into space, taking the Moon with it.
What about the Sun? Is it possible for the Earth to eventually lock gravitationally to the Sun?
Astronomers have found extrasolar planets orbiting other stars which are tidally locked. But they’re extremely close, well within the orbit of Mercury.
Here in our Solar System, we’re just too far away from the Sun for the Earth to lock to it. The gravitational influence of the other planets like Venus, Mars and Jupiter perturb our orbit and keep us from ever locking. Without any other planets in the Solar System, though, and with a Sun that would last forever, it would be an inevitability.
It is theoretically possible that the Earth will tidally lock to the Moon in about 50 billion years or so. Assuming the Earth and Moon weren’t consumed during the Sun’s red giant phase. I guess we’ll have to wait and see.
Venus is often referred to as “Earth’s Twin” (or “sister planet”), and for good reason. Despite some rather glaring differences, not the least of which is their vastly different atmospheres, there are enough similarities between Earth and Venus that many scientists consider the two to be closely related. In short, they are believed to have been very similar early in their existence, but then evolved in different directions.
Earth and Venus are both terrestrial planets that are located within the Sun’s Habitable Zone (aka. “Goldilocks Zone”) and have similar sizes and compositions. Beyond that, however, they have little in common. Let’s go over all their characteristics, one by one, so we can in what ways they are different and what ways they are similar.
Visible, infrared, and X-ray light image of Kepler's supernova remnant (SN 1604) located about 13,000 light-years away. Credit: NASA, ESA, R. Sankrit and W. Blair (Johns Hopkins University).
We all know that we are “made of star-stuff,” with all of the elements necessary for the formation of planets and even life itself having originated inside generations of massive stars, which over billions of years have blasted their creations out into the galaxy at the explosive ends of their lives. Supernovas are some of the most powerful and energetic events in the known Universe, and when a dying star finally explodes you wouldn’t want to be anywhere nearby—fresh elements are nice and all but the energy and radiation from a supernova would roast any planets within tens if not hundreds of light-years in all directions. Luckily for us we’re not in an unsafe range of any supernovas in the foreseeable future, but there was a time geologically not very long ago that these stellar explosions are thought to have occurred in nearby space… and scientists have recently found the “smoking gun” evidence at the bottom of the ocean.
Two independent teams of “deep-sea astronomers”—one led by Dieter Breitschwerdt from the Berlin Institute of Technology and the other by Anton Wallner from the Australian National University—have investigated sediment samples taken from the floors of the Pacific, Atlantic, and Indian oceans. The sediments were found to contain relatively high levels of iron-60, an unstable isotope specifically created during supernovas.
The Local Bubble is a 300-light-year long region that was carved out of the interstellar medium by supernovas (Source: Science@NASA)
The teams found that the ages of the iron-60 concentrations (the determination of which was recently perfected by Wallner) centered around two time periods, 1.7 to 3.2 million years ago and 6.5 to 8.7 million years ago. Based on this and the fact that our Solar System currently resides within a peanut-shaped region virtually empty of interstellar gas known as the Local Bubble, the researchers are confident that this provides further evidence that supernovas exploded within a mere 330 light-years of Earth, sending their elemental fallout our way.
“This research essentially proves that certain events happened in the not-too-distant past,” said Adrian Melott, an astrophysicist and professor at the University of Kansas who was not directly involved with the research but published his take on the findings in a letter in Nature. (Source)
The researchers think that two supernova events in particular were responsible for nearly half of the iron-60 concentrations now observed. These are thought to have taken place among a a nearby group of stars known as the Scorpius–Centaurus Association, some 2.3 and 1.5 million years ago. At those same time frames Earth was entering a phase of repeated global glaciation, the end of the last of which led to the rise of modern human civilization.
While supernovas of those sizes and distances wouldn’t have been a direct danger to life here on Earth, could they have played a part in changing the climate?
“Our local research group is working on figuring out what the effects were likely to have been,” Melott said. “We really don’t know. The events weren’t close enough to cause a big mass extinction or severe effects, but not so far away that we can ignore them either. We’re trying to decide if we should expect to have seen any effects on the ground on the Earth.”
Regardless of the correlation, if any, between ice ages and supernovas, it’s important to learn how these events do affect Earth and realize that they may have played an important and perhaps overlooked role in the history of life on our planet.
“Over the past 500 million years there must have been supernovae very nearby with disastrous consequences,” said Melott. “There have been a lot of mass extinctions, but at this point we don’t have enough information to tease out the role of supernovae in them.”
You can find the teams’ papers in Nature here and here.
UPDATE 4/14/16: The presence of iron-60 from the same time periods as those mentioned above has also been found on the Moon by research teams in Germany and the U.S. Read more here.
The Earth's layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com
Like all the other terrestrial planets, (Mercury, Venus, and Mars) the Earth is made up of many layers. This is the result of it undergoing planetary differentiation, where denser materials sink to the center to form the core while lighter materials form around the outside. Whereas the core is composed primarily of iron and nickel, Earth’s upper layer are composed of silicate rock and minerals.
This region is known as the mantle, and accounts for the vast majority of the Earth’s volume. Movement, or convection, in this layer is also responsible for all of Earth’s volcanic and seismic activity. Information about structure and composition of the mantle is either the result of geophysical investigation or from direct analysis of rocks derived from the mantle, or exposed mantle on the ocean floor.
What if someone were to tell you that at any given moment, you were traveling at speeds well in excess of the speed of sound? You might think they were crazy, given that – as best as you could tell – you were standing on solid ground, and not in the cockpit of a supersonic jet. Nevertheless, the statement is correct. At any given moment, we are all moving at a speed of about 1,674 kilometers an hour, thanks to the Earth’s rotation,
By definition, the Earth’s rotation is the amount of time that it takes to rotate once on its axis. This is, apparently, accomplished once a day – i.e. every 24 hours. However, there are actually two different kinds of rotation that need to be considered here. For one, there’s the amount of time it take for the Earth to turn once on its axis so that it returns to the same orientation compared to the rest of the Universe. Then there’s how long it takes for the Earth to turn so that the Sun returns to the same spot in the sky.
Our Sun in all its intense, energetic glory. When life appeared on Earth, the Sun would have been much different than it is now; a more intense, energetic neighbor. Image: NASA/SDO.
The early Solar System was a much different place than it is now. Chaos reigned supreme before things settled down into their present state. New research shows that the young Sun was more chaotic and expressive than it is now, and that Earth’s magnetic field was key for the development of life on Earth.
Researchers at the Harvard Smithsonian Centre for Astrophysics have been studying a star called Kappa Ceti, about 30 light years away in the Cetus constellation. Kappa Ceti is in many ways similar to our own Sun, but it’s estimated to be between 400 million to 600 million years old, about the same age as our Sun when life appeared on Earth. Studying Kappa Ceti gives scientists a good idea of the type of star that early life on Earth had to contend with.
Kappa Ceti, at its young age, is much more magnetically active than our 4.6 billion year old Sun, according to this new research. It emits a relentless solar wind, which the research team at Harvard says is 50 times as powerful as the solar wind from our Sun. It’s surface is also much more active and chaotic. Rather than the sunspots that we can see on our Sun, Kappa Ceti displays numerous starspots, the larger brother of the sunspot. And the starspots on Kappa Ceti are much more numerous than the sunspots observed on the Sun.
We’re familiar with the solar flares that come from the Sun periodically, but in the early life of the Sun, the flares were much more energetic too. Researchers have found evidence on Kappa Ceti of what are called super-flares. These monsters are similar to the flares we see today, but can release 10 to 100 million times more energy than the flares we can observe on our Sun today.
So if early life on Earth had to contend with such a noisy neighbour for a Sun, how did it cope? What prevented all that solar output from stripping away Earth’s atmosphere, and killing anything alive? Then, as now, the Earth’s electromagnetic field protected it. But in the same way that the Sun was so different long ago, so was the Earth’s protective shield. It may have been weaker than it is now.
The researchers found that if the Earth’s magnetic field was indeed weaker, then the magnetosphere may have been only 34% to 48% as large as it is now. The conclusion of the study says “… the early magnetic interaction between the stellar wind and the young Earth planetary magnetic field may well have prevented the volatile losses from the Earth exosphere and created conditions to support life.”
Or, in plain language: “The early Earth didn’t have as much protection as it does now, but it had enough,” says Do Nascimento.
The Moon's shadow is cast across Indonesia in this view from the DSCOVR spacecraft, March 9, 2016. (Courtesy of the DSCOVR EPIC team.)
On March 8, 2016 (March 9 local time) the Moon briefly blocked the light from the Sun in what was the only total solar eclipse of the year. The event was visible across portions of southeast Asia, Indonesia, and Micronesia, and was observed by both skywatchers on the ground in person and those watching live online around the world. While to most the view was of a silhouetted Moon slowly carving away the disk of the Sun before totality revealed a shimmering corona, the view from space looking back at Earth showed the Moon’s dark shadow passing over islands, clouds, and sea.
An artist's image of an asteroid Impact. Image Credit: University of California Observatories/Don Davis.
All over the Earth, there is a buried layer of sediment rich in iridium called the Cretaceous Paleogene-Boundary (K-Pg.) This sediment is the global signature of the 10-km-diameter asteroid that killed off the dinosaurs—and about 50% of all other species—66 million years ago. Now, in an effort to understand how life recovered after that event, scientists are going to drill down into the site where the asteroid struck—the Chicxulub Crater off the coast of Mexico’s Yucatan Peninsula.
The end-Cretaceous extinction was a global catastrophe, and a lot is already known about it. We’ve learned a lot about the physical effects of the strike on the impact area from oil and gas drilling in the Gulf of Mexico. According to data from that drilling, released on February 5th in the Journal of Geophysical Research: Solid Earth, the asteroid that struck Earth displaced approximately 200,000 cubic km (48,000 cubic miles) of sediment. That’s enough to fill the largest of the Great Lakes—Lake Superior—17 times.
The Chicxulub impact caused earthquakes and tsunamis that first loosened debris, then swept it from nearby areas like present-day Florida and Texas into the Gulf basin itself. This layer is hundreds of meters thick, and is hundreds of kilometers wide. It covers not only the Gulf of Mexico, but also the Caribbean and the Yucatan Peninsula.
In April, a team of scientists from the University of Texas and the National University of Mexico will spend two months drilling in the area, to gain insight into how life recovered after the impact event. Research Professor Sean Gulick of the University of Texas Institute for Geophysics told CNN in an interview that the team already has a hypothesis for what they will find. “We expect to see a period of no life initially, and then life returning and getting more diverse through time.”
Scientists have been wanting to drill in the impact region for some time, but couldn’t because of commercial drilling activity. Allowing this team to study the region directly will build on what is already known: that this enormous deposit of sediment happened over a very short period of time, possibly only a matter of days. The drilling will also help paint a picture of how life recovered by looking at the types of fossils that appear. Some scientists think that the asteroid impact would have lowered the pH of the oceans, so the fossilized remains of animals that can endure greater acidity would be of particular interest.
The Chicxulub impact was a monumental event in the history of the Earth, and it was extremely powerful. It may have been a billion times more powerful than the atomic bomb dropped on Hiroshima. Other than the layer of sediment laid down near the site of the impact itself, its global effects probably included widespread forest fires, global cooling from debris in the atmosphere, and then a period of high temperatures caused by an increase in atmospheric CO2.
We already know what will happen if an asteroid this size strikes Earth again—global devastation. But drilling in the area of the impact will tell us a lot about how geological and ecological processes respond to this type of devastation.
The eight planets of our Solar System vary widely, not only in terms of size, but also in terms of mass and density (i.e. its mass per unit of volume). For instance, the 4 inner planets – those that are closest to the Sun – are all terrestrial planets, meaning they are composed primarily of silicate rocks or metals and have a solid surface. On these planets, density varies the farther one ventures from the surface towards the core, but not considerably.
By contrast, the 4 outer planets are designated as gas giants (and/or ice giants) which are composed primarily of of hydrogen, helium, and water existing in various physical states. While these planets are greater in size and mass, their overall density is much lower. In addition, their density varies considerably between the outer and inner layers, ranging from a liquid state to materials so dense that they become rock-solid.
