Tag Archives: habitable

New study lists 24 exoplanets that may be better for life than Earth

Although we’re all from here, Earth isn’t necessarily the best planet to live on in the Universe, according to new research. A new study lists two dozen such “superhabitable” planet candidates for further research.

Image via Pixabay.

It is quite an unexpected turn of events, but the planets identified in the new study all show some properties that could make it a better home for earthlings than Earth itself.

The study, published by researchers from Washington State University, also detail why these planets were chosen. Some are older, some larger, others wetter and slightly warmer than Earth. Some of them even orbit ‘better’ stars than our own Sun, and are expected to exist for longer.

Better than the original

“With the next space telescopes coming up, we will get more information, so it is important to select some targets,” said Schulze-Makuch, a professor with WSU and the Technical University in Berlin.

“We have to focus on certain planets that have the most promising conditions for complex life. However, we have to be careful to not get stuck looking for a second Earth because there could be planets that might be more suitable for life than ours.”

All the 24 maybe-superhabitable planets are over 100 light years away from Earth, so for the time being, they’re far beyond our grasp. However, with concentrated effort and data pooled from current and future telescopes, such as from NASA’s James Webb Space Telescope, the LUVIOR space observatory, and the European Space Agency’s PLATO space telescope, we could glean enough data to see whether they’d be nice places to live.

Schulze-Makuch, a geobiologist with expertise in planetary habitability, worked with astronomers René Heller of the Max Planck Institute for Solar System Research and Edward Guinan of Villanova University to first determine which criteria would make a planet superhabitable. Then, they dredged through data of the over 4,500 known exoplanets to see which would fit.

A habitable planet isn’t necessarily one that has life, but one that has the right conditions to sustain life as we know it — things like pleasant temperatures, liquid water, magnetic fields, and breathable atmosphere.

The team looked at systems with stars similar to our Sun (G-class stars) and planets orbiting them in the liquid water zone — not too far nor too close. But since G-class stars have a lifespan of just 10 billion years, and it took life on Earth 4 billion years to evolve, this means they’re not the best candidates for life, as they can consume their fuel before anything spawns on the planets that orbit them. That’s why the team also looked at the cooler, dimmer K-class dwarf stars, which have lifespans of 20 billion to 70 billion years.

While this gives the planets more time to develop life, the authors argue that we shouldn’t be looking at ones that are too old. In order to be habitable, a planet needs a protective magnetic field — the ones that don’t end up like Mars is today. Those magnetic fields are generated in their core, and they’re powered by geothermal energy — which itself is produced by radioactive decay inside the planet. The Earth is around 4.5 billion years old, meaning it hasn’t yet expended its cache of geothermal energy. The authors thus argue that we should be looking for exoplanets 5 billion to 8 billion years old.

As far as size is concerned, we should look for something slightly larger and heavier than our own. Exoplanets that are at least 10% larger than Earth would have more habitable land but provide almost the same experience as living here. One around 1.5 times heavier should be able to better retain its geothermal energy and have enough gravity to keep its atmosphere intact.

Size and mass also matter. A planet that is 10% larger than the Earth should have more habitable land. One that is about 1.5 times Earth’s mass would be expected to retain its interior heating through radioactive decay longer and would also have a stronger gravity to retain an atmosphere over a longer time period.

Another element they’d look for is more water, especially in the form of moisture, clouds, and atmospheric humidity. A surface temperature of around 5 degrees Celsius (8 Fahrenheit) higher than on Earth, alongside extra moisture, would probably be better suited to life as we know it today. They argue that these elements make rainforests on Earth more biodiverse than forests in colder, drier areas.

None of the 24 exoplanets meet all the criteria, but one of the candidates has four.

“It’s sometimes difficult to convey this principle of superhabitable planets because we think we have the best planet,” said Schulze-Makuch.

“We have a great number of complex and diverse lifeforms, and many that can survive in extreme environments. It is good to have adaptable life, but that doesn’t mean that we have the best of everything.”

The paper “In Search for a Planet Better than Earth: Top Contenders for a Superhabitable World” has been published in the journal Astrobiology.

Venus could once have been a very welcoming planet, NASA study found

Our closest neighboring planet, Venus, is not a place you’d like to visit. Scorching surface temperatures, an atmosphere so dense it would crush your bones, and acid thunderstorms. It’s about as far from a life-friendly planet as you could get. But, a NASA research team proposes that Venus’ hellish surface used to be very comfortable and pristine — up until some 700 million years ago.

Image credits Mattias Malmer/NASA/JPL.

“Both planets probably enjoyed warm liquid water oceans in contact with rock and with organic molecules undergoing chemical evolution in those oceans,” David Grinspoon at the Planetary Science Institute in Tucson, Arizona told Aviva Rutkin at New Scientist.

“As far as we understand at present, those are the requirements for the origin of life.”

Venus has all the makings of a planet that should sustain life: it’s very similar in size, density, and chemical composition to our own planet. Its proximity to Earth further suggests that the two planets were formed from the same primordial materials.

“Venus also has an unusually high ratio of deuterium to hydrogen atoms, a sign that it once housed a substantial amount of water, mysteriously lost over time,” says Rutkin.

But at surface level, the two planets couldn’t be more different. Venus is the hottest planet in the Solar System, so hot in fact that rainfall on the planet evaporates before reaching the ground. This is probably for the best as it rains sulphuric acid, not water, on Venus. Its lightning-and-greenhouse-gas-choked atmosphere is dense enough that carbon dioxide becomes liquid at ground level, so potential human visitors would have a very pressing need for protection.

Still, researchers believe that Venus wasn’t always the hellish place we see today. A recent NASA study lends weight to this theory, showing that up to 3 billion years ago the planet could have had mild, Earth-like temperatures and bodies of water.

Michael Way and his team from the NASA Goddard Institute for Space Studies simulated four versions of early Venus, each with slightly altered factors — such as length of days, incoming energy from the Sun, etc. Left to cook for a few billions of years, the most promising model evolved to have moderate surface temperatures, dense cloud cover to protect the surface from solar radiation, even snow. This model produces habitable conditions in 2-billion-year stretches and estimates that the planet remained habitable up to 715 million years ago.

One catch is that for the model to work, it requires Venus to have been spinning as slowly as it does today – something that researchers have yet to prove. We know that Earth’s rotation has been steadily slowing down over time, and some researchers argue that the same could be true for Venus.

“If Venus was spinning more rapidly, all bets are off,” said Michael Way.

“But, under the right conditions, “You get temperatures almost like Earth. That’s remarkable.”

If the models are accurate, however, the implications could be huge — a few billion years is more than enough time for life to have evolved on Venus during its milder days. Unfortunately, the Venus of today doesn’t really lend well to searching for clues of long-lost life. And we don’t know why it got this way, we don’t know what or when went wrong.

“It’s one of the big mysteries about Venus. How did it get so different from Earth when it seems likely to have started so similarly? The question becomes richer when you consider astrobiology, the possibility that Venus and Earth were very similar during the time of the origin of life on Earth,” Grinspoon said.

The only way to find out if Venus was ever habitable, if life ever evolved here, to figure out what happened for it to end up as it is, is to go there and poke around — something that NASA is already considering.

The full paper, “Was Venus the First Habitable World of our Solar System?” has been accepted for publication in Geophysical Research Letters.

The Kepler mission: searching for planets in the Goldilocks area

The Goldilocks area is one of the most interesting for astronomers throughout the known Universe, as it has great hope for finding planets similar to our Earth. The Kepler 10b planet is not the most hospitable one you could think of: located some 560 million light years away from our planet, and with a surface temperature hot enough to melt steel, it is however the first one located with the Kepler space telescope, which was launched by NASA with the role of finding habitable planets in the Goldilocks area, not too cold and not too hot; many have nicknamed it Hubble’s smaller brother.

Since the first planet beyond our solar system has been found in 1992, it’s been pretty much of a roll, with the count now being over 500, and the finds will grow a whole lot in the near future, partially thanks to the Kepler telescope; one of the leading astronomers of the project is Geoff Marcy, who helped spot 70 planets out of the first 100 ever to be found.

What sometimes gets lost in the shuffle when a nice result shows up on all of the Web pages and the newspapers around the world — what you don’t realize is to get that result meant that five or 10 people were burning that midnight oil, trimming the errors down to the point that the Earth-size planets are detectable. It’s easy to dismiss the discoveries as, Oh, it’s new computers, or it’s new optics. These things happen because amazing people dream and then put their dreams into perspiration-dripping action.

He also seems very optimistic about the future of Kepler, and for good reason: just this week he managed to find nine planets, and this is just the beginning.

“Honestly, Kepler’s so good that it’s hard to beat it. It gets the numbers. Kepler’s going to find thousands. There’s going to be another follow-up to Kepler, either from Europe or the U.S. or both. They’ll find thousands. I bet by 2020, there’ll be 10,000 planets, and by 2030 there might be another 20,000 or 30,000 more planets.”

The bad news is that the number of the planets will find will plateau, and not grow exponentially; the good news is that it’s not the numbers we should be looking at increasing, it’s the quality of the findings. We should be looking at planets with an atmosphere, and with a temperature between the freezing and boiling point. The odds of life on Earth may be one in a billion, but there are a lot more than 1 billion planets out there, so if we keep looking, we’re bound to find something.

Water and fog found on Titan, Saturn’s moon

As I was writing in a previous post, Titan is quite unique, in that aside from our planet it’s the only place in our solar system where significant quantities of liquid are to be found (though most are liquid ethane and methane). That doesn’t seem to make much of a difference considering the chemistry of it, but according to astronomer Mike Brown of the California Institute of Technology (Caltech) mother Earth and Saturn’s moon share another important characteristic: they have common fog. That implies there is an exchange of material between the atmosphere and the planet surface, a phenomenon previously only known to take place on our planet. It also shows there is an active hydrological cycle taking place.


The Cassini probe has once again proven it’s value; the Visual and Infrared Mapping Spectrometer (VIMS) onboard the probe provided the data that eventually led to this conclusion. They found what could be described as isolated clouds at approximately 750 meters above the surface, and not higher, where clouds are usually formed. So the conclusion was simple: they found fog.

“Fog—or clouds, or dew, or condensation in general—can form whenever air reaches about 100 percent humidity,” Brown says. “There are two ways to get there. The first is obvious: add water (on Earth) or methane (on Titan) to the surrounding air. The second is much more common: make the air colder so it can hold less water (or liquid methane), and all of that excess needs to condense.”

Illustration of a view from Titan

Illustration of a view from Titan

He explains that this is the exact same process that causes water droplets to take shape on the outside of a very cool glass.

“That fog you often see at sunrise hugging the ground is caused by ground-level air cooling overnight, to the point where it cannot hang onto its water. As the sun rises and the air heats, the fog goes away.”

However, for some reason, this mechanism doesn’t work on Titan because the planet’s atmosphere causes extremely slow cooling or warming.

“If you were to turn the sun totally off, Titan’s atmosphere would still take something like 100 years to cool down,” Brown says. “Even the coldest parts of the surface are much too warm to ever cause fog to condense.”

He was asked if it could be all about mountain fog, but he rejected this categorically.

“A Titanian mountain would have to be about 15,000 feet high before the air would get cold enough to condense,” he says