November 22, 2017

How we can build another Earth

Earth

People dream of traveling to the stars. Movies like Interstellar and Avatar, and hundreds of other captivating science fiction stories, paint a picture as to what might be out there.

But will space travel to worlds beyond our Solar System ever become a reality?
Astronomers made a giant leap forward for the dreams of space travel with the discovery of a planet around the very nearest star to our sun — Proxima Centauri. “Near” is a relative term. At 25 trillion miles away, Proxima is still far out of reach for human space travel.
Proxima Centauri b orbits within its star’s “Goldilocks Zone.” As heated by the star, the planet’s surface might be not too hot, not too cold but just right for life, if the planet has an atmosphere like Earth’s.
But that is a huge “if.”
The planet Proxima Centauri b may have an atmosphere very different from Earth’s. Too much of a greenhouse effect or not enough. A massive crushing atmosphere or almost none at all. The atmosphere acts like a blanket to control the surface temperature. If we are to ever travel to a distant world, it needs to be one where the atmosphere can create a surface temperature to support liquid water—needed for all life as we know it.
Searching for Earth-like worlds
As an astrophysicist I research exoplanet atmospheres and have invented methods to learn more about them. We call our methods “remote sensing” because we gather information from afar, using Hubble and other telescopes in space and on the ground. We astronomers have so far observed dozens of exoplanet atmospheres—albeit hot or large or otherwise completely uninhabitable planets.
We are now excitedly yet impatiently waiting to get our hands on data of Proxima Centauri b and other rocky planets in its star’s Goldilocks zone. New, highly capable telescopes are coming online in the next two to 10 years to help start the job.
We will first look for water vapor in the planet’s atmosphere — suggestive of liquid water oceans. We will be ecstatic to find oxygen, a tell-tale sign of life, and something we humans need to breathe to survive. Finding ozone, a byproduct of oxygen, would be a relief as ozone creates a high atmospheric layer that protects the planet surface from harmful high-energy radiation emitted by the star. We will aim to make an inventory of other gases such as carbon dioxide and methane, to help us understand the greenhouse power of the atmosphere.
I am fully confident we will be able to identify the basic information about a distant world. But, the planets are so far away and so small and faint that we will not have all the information our descendants will need to know if humans can survive or thrive on the distant world. Are there fatally poisonous gases that elude remote sensing detection? Can the soil chemistry support the crops we want to grow? If there is oxygen, is it the right amount, or too much so as to be harmful?
Transforming and terraforming planets
Our descendants will need to geoengineer their surroundings, to remove or add atmospheric gases and to change some chemical properties of the oceans and soils. On Earth we already have what could be considered fledgling efforts and concepts: carbon sequestration to reduce the amount of carbon dioxide; desalination of oceans for drinking water; and even cloud seeding for rain.
Consider for a moment that nature does not provide a nearby planet with anything close to Earth-like conditions. Not Proxima Centauri b, nor any other nearby Goldilocks Zone rocky world we are working so hard to find. Instead of just tweaking the planet conditions our descendants will need to terraform — completely transform a planet’s atmosphere and surface by large planetary-scale engineering.
There are already definitive ideas for terraforming Mars we could borrow from, for a too cold planet with a thin atmosphere.
One of my favorites is to unfurl a large reflective screen that orbits the planet and bounces starlight (the host “sunlight”) to warm the planet’s surface, melting ice caps of frozen carbon dioxide and water. This would literally create an atmosphere — a stable greenhouse atmosphere that enables the right surface pressure for liquid water to exist. To get oxygen, we could seed the planet with oxygen-producing cyanobacteria, perhaps even in advance of our arrival.
Super space travelers of the future
But there may be bigger problems for our future travelers. A crushing surface gravity making it too hard to walk around or to do work. Unpredictable bursts of extreme UV and other highly damaging radiation from stellar flares that are common on stars like Proxima Centauri.
So I imagine a more fantastic future, borne out by a promise of biology to someday control our own genetics.

‘How we can build another Earth’
Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth.
Photos: Weird and wonderful planets beyond our solar system
Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth.

This Jupiter-like planet in the HD-188753 system, 149 light-years from Earth, has three suns. The main star is similar in mass to our own Sun. The system has been compared to Luke Skywalker's home planet Tatooine in "Star Wars."
Photos: Weird and wonderful planets beyond our solar system
This Jupiter-like planet in the HD-188753 system, 149 light-years from Earth, has three suns. The main star is similar in mass to our own Sun. The system has been compared to Luke Skywalker’s home planet Tatooine in “Star Wars.”

Kepler-421b is a Uranus-sized transiting exoplanet with the longest known year, as it circles its star once every 704 days. The planet orbits an orange, K-type star that is cooler and dimmer than our Sun and is located about 1,000 light-years from Earth in the constellation Lyra.
Photos: Weird and wonderful planets beyond our solar system
Kepler-421b is a Uranus-sized transiting exoplanet with the longest known year, as it circles its star once every 704 days. The planet orbits an orange, K-type star that is cooler and dimmer than our Sun and is located about 1,000 light-years from Earth in the constellation Lyra.

Astronomers discovered two planets less than three times the size of Earth orbiting sun-like stars in a crowded stellar cluster approximately 3,000 light-years from Earth in the constellation Cygnus.
Photos: Weird and wonderful planets beyond our solar system
Astronomers discovered two planets less than three times the size of Earth orbiting sun-like stars in a crowded stellar cluster approximately 3,000 light-years from Earth in the constellation Cygnus.

This artist's conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. The majority of the sun's closest stellar neighbors are red dwarfs.
Photos: Weird and wonderful planets beyond our solar system
This artist’s conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. The majority of the sun’s closest stellar neighbors are red dwarfs.

Kepler-186f was the first validated Earth-sized planet to be found orbiting a distant star in the habitable zone. This zone a range of distance from a star where liquid water might pool on the planet's surface.
Photos: Weird and wonderful planets beyond our solar system
Kepler-186f was the first validated Earth-sized planet to be found orbiting a distant star in the habitable zone. This zone a range of distance from a star where liquid water might pool on the planet’s surface.

Kepler-69c is a super-Earth-size planet similar to Venus. The planet is found in the habitable zone of a star like our sun, approximately 2,700 light years from Earth in the constellation Cygnus.
Photos: Weird and wonderful planets beyond our solar system
Kepler-69c is a super-Earth-size planet similar to Venus. The planet is found in the habitable zone of a star like our sun, approximately 2,700 light years from Earth in the constellation Cygnus.

The Kepler-444 system formed when the Milky Way was just 2 billion years old. The tightly packed system is home to five planets that range in size, the smallest is comparable to the size of Mercury and the largest to Venus, orbiting their sun in less than 10 days.
Photos: Weird and wonderful planets beyond our solar system
The Kepler-444 system formed when the Milky Way was just 2 billion years old. The tightly packed system is home to five planets that range in size, the smallest is comparable to the size of Mercury and the largest to Venus, orbiting their sun in less than 10 days.

This artistic concept image compares Earth, left, with Kepler-452b, which is about 60% larger. Both planets orbit a G2-type star of about the same temperature; however, the star hosting Kepler-452b is 6 billion years old — 1.5 billion years older than our sun.
Photos: Weird and wonderful planets beyond our solar system
This artistic concept image compares Earth, left, with Kepler-452b, which is about 60% larger. Both planets orbit a G2-type star of about the same temperature; however, the star hosting Kepler-452b is 6 billion years old — 1.5 billion years older than our sun.

Artist's conception of the binary system with three giant planets discovered, where one star hosts two planets and the other hosts the third. The system represents the smallest-separation binary in which both stars host planets that has ever been observed.
Photos: Weird and wonderful planets beyond our solar system
Artist’s conception of the binary system with three giant planets discovered, where one star hosts two planets and the other hosts the third. The system represents the smallest-separation binary in which both stars host planets that has ever been observed.

This artist's impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system.
Photos: Weird and wonderful planets beyond our solar system
This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system.

This artist's impression shows a view of the surface of the planet Proxima b.
Photos: Weird and wonderful planets beyond our solar system
This artist’s impression shows a view of the surface of the planet Proxima b.

An artist's rendering shows Earth-sized exoplanets TRAPPIST-1b and 1c in a rare double transit event as they pass in front of their ultracool red dwarf star, which allowed Hubble to take a peek at at their atmospheres.
Photos: Weird and wonderful planets beyond our solar system
An artist’s rendering shows Earth-sized exoplanets TRAPPIST-1b and 1c in a rare double transit event as they pass in front of their ultracool red dwarf star, which allowed Hubble to take a peek at at their atmospheres.

Out of a new discovery of 104 exoplanets, astronomers found four similar in size to Earth that are orbiting a dwarf star. Two of them have the potential to support life. The craft depicted in this illustration is the NASA Kepler Space Telescope, which has helped confirm the existence of thousands of exoplanets.
Photos: Weird and wonderful planets beyond our solar system
Out of a new discovery of 104 exoplanets, astronomers found four similar in size to Earth that are orbiting a dwarf star. Two of them have the potential to support life. The craft depicted in this illustration is the NASA Kepler Space Telescope, which has helped confirm the existence of thousands of exoplanets.

This artist's impression shows a view of the triple-star system HD 131399 from close to the giant planet orbiting in the system. Located about 320 light-years from Earth, the planet is about 16 million years old, making it also one of the youngest exoplanets discovered to date.
Photos: Weird and wonderful planets beyond our solar system
This artist’s impression shows a view of the triple-star system HD 131399 from close to the giant planet orbiting in the system. Located about 320 light-years from Earth, the planet is about 16 million years old, making it also one of the youngest exoplanets discovered to date.

An artistic impression of the planet Kepler-1647b, which is nearly identical to Jupiter in both size and mass. The planet is expected to be roughly similar in appearance. But it is much warmer: Kepler-1647b is in the habitable zone.
Photos: Weird and wonderful planets beyond our solar system
An artistic impression of the planet Kepler-1647b, which is nearly identical to Jupiter in both size and mass. The planet is expected to be roughly similar in appearance. But it is much warmer: Kepler-1647b is in the habitable zone.

HD-106906b is a gaseous planet 11 times more massive than Jupiter. The planet is believed to have formed in the center of its solar system, before being sent flying out to the edges of the region by a violent gravitational event.
Photos: Weird and wonderful planets beyond our solar system
HD-106906b is a gaseous planet 11 times more massive than Jupiter. The planet is believed to have formed in the center of its solar system, before being sent flying out to the edges of the region by a violent gravitational event.

Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth.
Photos: Weird and wonderful planets beyond our solar system
Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth.

This Jupiter-like planet in the HD-188753 system, 149 light-years from Earth, has three suns. The main star is similar in mass to our own Sun. The system has been compared to Luke Skywalker's home planet Tatooine in "Star Wars."
Photos: Weird and wonderful planets beyond our solar system
This Jupiter-like planet in the HD-188753 system, 149 light-years from Earth, has three suns. The main star is similar in mass to our own Sun. The system has been compared to Luke Skywalker’s home planet Tatooine in “Star Wars.”

Kepler-421b is a Uranus-sized transiting exoplanet with the longest known year, as it circles its star once every 704 days. The planet orbits an orange, K-type star that is cooler and dimmer than our Sun and is located about 1,000 light-years from Earth in the constellation Lyra.
Photos: Weird and wonderful planets beyond our solar system
Kepler-421b is a Uranus-sized transiting exoplanet with the longest known year, as it circles its star once every 704 days. The planet orbits an orange, K-type star that is cooler and dimmer than our Sun and is located about 1,000 light-years from Earth in the constellation Lyra.

Astronomers discovered two planets less than three times the size of Earth orbiting sun-like stars in a crowded stellar cluster approximately 3,000 light-years from Earth in the constellation Cygnus.
Photos: Weird and wonderful planets beyond our solar system
Astronomers discovered two planets less than three times the size of Earth orbiting sun-like stars in a crowded stellar cluster approximately 3,000 light-years from Earth in the constellation Cygnus.

This artist's conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. The majority of the sun's closest stellar neighbors are red dwarfs.
Photos: Weird and wonderful planets beyond our solar system
This artist’s conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. The majority of the sun’s closest stellar neighbors are red dwarfs.

Kepler-186f was the first validated Earth-sized planet to be found orbiting a distant star in the habitable zone. This zone a range of distance from a star where liquid water might pool on the planet's surface.
Photos: Weird and wonderful planets beyond our solar system
Kepler-186f was the first validated Earth-sized planet to be found orbiting a distant star in the habitable zone. This zone a range of distance from a star where liquid water might pool on the planet’s surface.

Kepler-69c is a super-Earth-size planet similar to Venus. The planet is found in the habitable zone of a star like our sun, approximately 2,700 light years from Earth in the constellation Cygnus.
Photos: Weird and wonderful planets beyond our solar system
Kepler-69c is a super-Earth-size planet similar to Venus. The planet is found in the habitable zone of a star like our sun, approximately 2,700 light years from Earth in the constellation Cygnus.

The Kepler-444 system formed when the Milky Way was just 2 billion years old. The tightly packed system is home to five planets that range in size, the smallest is comparable to the size of Mercury and the largest to Venus, orbiting their sun in less than 10 days.
Photos: Weird and wonderful planets beyond our solar system
The Kepler-444 system formed when the Milky Way was just 2 billion years old. The tightly packed system is home to five planets that range in size, the smallest is comparable to the size of Mercury and the largest to Venus, orbiting their sun in less than 10 days.

This artistic concept image compares Earth, left, with Kepler-452b, which is about 60% larger. Both planets orbit a G2-type star of about the same temperature; however, the star hosting Kepler-452b is 6 billion years old — 1.5 billion years older than our sun.
Photos: Weird and wonderful planets beyond our solar system
This artistic concept image compares Earth, left, with Kepler-452b, which is about 60% larger. Both planets orbit a G2-type star of about the same temperature; however, the star hosting Kepler-452b is 6 billion years old — 1.5 billion years older than our sun.

conception of the binary system with three giant planets discovered, where one star hosts two planets and the other hosts the third. The system represents the smallest-separation binary in which both stars host planets that has ever been observed.
Photos: Weird and wonderful planets beyond our solar system
Artist’s conception of the binary system with three giant planets discovered, where one star hosts two planets and the other hosts the third. The system represents the smallest-separation binary in which both stars host planets that has ever been observed.

This artist's impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system.
Photos: Weird and wonderful planets beyond our solar system
This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system.

This artist's impression shows a view of the surface of the planet Proxima b.
Photos: Weird and wonderful planets beyond our solar system
This artist’s impression shows a view of the surface of the planet Proxima b.

An artist's rendering shows Earth-sized exoplanets TRAPPIST-1b and 1c in a rare double transit event as they pass in front of their ultracool red dwarf star, which allowed Hubble to take a peek at at their atmospheres.
Photos: Weird and wonderful planets beyond our solar system
An artist’s rendering shows Earth-sized exoplanets TRAPPIST-1b and 1c in a rare double transit event as they pass in front of their ultracool red dwarf star, which allowed Hubble to take a peek at at their atmospheres.

Out of a new discovery of 104 exoplanets, astronomers found four similar in size to Earth that are orbiting a dwarf star. Two of them have the potential to support life. The craft depicted in this illustration is the NASA Kepler Space Telescope, which has helped confirm the existence of thousands of exoplanets.
Photos: Weird and wonderful planets beyond our solar system
Out of a new discovery of 104 exoplanets, astronomers found four similar in size to Earth that are orbiting a dwarf star. Two of them have the potential to support life. The craft depicted in this illustration is the NASA Kepler Space Telescope, which has helped confirm the existence of thousands of exoplanets.

This artist's impression shows a view of the triple-star system HD 131399 from close to the giant planet orbiting in the system. Located about 320 light-years from Earth, the planet is about 16 million years old, making it also one of the youngest exoplanets discovered to date.
Photos: Weird and wonderful planets beyond our solar system
This artist’s impression shows a view of the triple-star system HD 131399 from close to the giant planet orbiting in the system. Located about 320 light-years from Earth, the planet is about 16 million years old, making it also one of the youngest exoplanets discovered to date.

An artistic impression of the planet Kepler-1647b, which is nearly identical to Jupiter in both size and mass. The planet is expected to be roughly similar in appearance. But it is much warmer: Kepler-1647b is in the habitable zone.
Photos: Weird and wonderful planets beyond our solar system
An artistic impression of the planet Kepler-1647b, which is nearly identical to Jupiter in both size and mass. The planet is expected to be roughly similar in appearance. But it is much warmer: Kepler-1647b is in the habitable zone.

HD-106906b is a gaseous planet 11 times more massive than Jupiter. The planet is believed to have formed in the center of its solar system, before being sent flying out to the edges of the region by a violent gravitational event.
Photos: Weird and wonderful planets beyond our solar system
HD-106906b is a gaseous planet 11 times more massive than Jupiter. The planet is believed to have formed in the center of its solar system, before being sent flying out to the edges of the region by a violent gravitational event.

Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth.
Photos: Weird and wonderful planets beyond our solar system
Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth.

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Story highlights
Will humans ever live on other planets? Asks astrophysicist Sara Seager
Future generations may need to terraform planets to make them habitable
We may see a future of bioengineered humans able to live on ‘unearthly’ planets
Sara Seager is a professor of Planetary Science and Physics at the Massachusetts Institute of Technology. The views expressed in this commentary are her ow People dream of traveling to the stars. Movies like Interstellar and Avatar, and hundreds of other captivating science fiction stories, paint a picture as to what might be out there.

But will space travel to worlds beyond our Solar System ever become a reality?
Astronomers made a giant leap forward for the dreams of space travel with the discovery of a planet around the very nearest star to our sun — Proxima Centauri. “Near” is a relative term. At 25 trillion miles away, Proxima is still far out of reach for human space travel.
Proxima Centauri b orbits within its star’s “Goldilocks Zone.” As heated by the star, the planet’s surface might be not too hot, not too cold but just right for life, if the planet has an atmosphere like Earth’s.
But that is a huge “if.”
Sara Seager is on a quest to find all of the "Earths next door"
Sara Seager is on a quest to find all of the “Earths next door”
The planet Proxima Centauri b may have an atmosphere very different from Earth’s. Too much of a greenhouse effect or not enough. A massive crushing atmosphere or almost none at all. The atmosphere acts like a blanket to control the surface temperature. If we are to ever travel to a distant world, it needs to be one where the atmosphere can create a surface temperature to support liquid water—needed for all life as we know it.
Searching for Earth-like worlds
As an astrophysicist I research exoplanet atmospheres and have invented methods to learn more about them. We call our methods “remote sensing” because we gather information from afar, using Hubble and other telescopes in space and on the ground. We astronomers have so far observed dozens of exoplanet atmospheres—albeit hot or large or otherwise completely uninhabitable planets.
We are now excitedly yet impatiently waiting to get our hands on data of Proxima Centauri b and other rocky planets in its star’s Goldilocks zone. New, highly capable telescopes are coming online in the next two to 10 years to help start the job.
Giant leaps in space exploration

Giant leaps in space exploration 00:55
We will first look for water vapor in the planet’s atmosphere — suggestive of liquid water oceans. We will be ecstatic to find oxygen, a tell-tale sign of life, and something we humans need to breathe to survive. Finding ozone, a byproduct of oxygen, would be a relief as ozone creates a high atmospheric layer that protects the planet surface from harmful high-energy radiation emitted by the star. We will aim to make an inventory of other gases such as carbon dioxide and methane, to help us understand the greenhouse power of the atmosphere.
Meet the artists who paint alien landscapes
Meet the artists who paint alien landscapes
I am fully confident we will be able to identify the basic information about a distant world. But, the planets are so far away and so small and faint that we will not have all the information our descendants will need to know if humans can survive or thrive on the distant world. Are there fatally poisonous gases that elude remote sensing detection? Can the soil chemistry support the crops we want to grow? If there is oxygen, is it the right amount, or too much so as to be harmful?
Transforming and terraforming planets
Our descendants will need to geoengineer their surroundings, to remove or add atmospheric gases and to change some chemical properties of the oceans and soils. On Earth we already have what could be considered fledgling efforts and concepts: carbon sequestration to reduce the amount of carbon dioxide; desalination of oceans for drinking water; and even cloud seeding for rain.
Consider for a moment that nature does not provide a nearby planet with anything close to Earth-like conditions. Not Proxima Centauri b, nor any other nearby Goldilocks Zone rocky world we are working so hard to find. Instead of just tweaking the planet conditions our descendants will need to terraform — completely transform a planet’s atmosphere and surface by large planetary-scale engineering.
There are already definitive ideas for terraforming Mars we could borrow from, for a too cold planet with a thin atmosphere.
Sara Seager — the planet hunter searching for another Earth

Sara Seager — the planet hunter searching for another Earth 01:39
One of my favorites is to unfurl a large reflective screen that orbits the planet and bounces starlight (the host “sunlight”) to warm the planet’s surface, melting ice caps of frozen carbon dioxide and water. This would literally create an atmosphere — a stable greenhouse atmosphere that enables the right surface pressure for liquid water to exist. To get oxygen, we could seed the planet with oxygen-producing cyanobacteria, perhaps even in advance of our arrival.
Super space travelers of the future
But there may be bigger problems for our future travelers. A crushing surface gravity making it too hard to walk around or to do work. Unpredictable bursts of extreme UV and other highly damaging radiation from stellar flares that are common on stars like Proxima Centauri.
So I imagine a more fantastic future, borne out by a promise of biology to someday control our own genetics.
Could humans live on newly discovered exoplanet?

Could humans live on newly discovered exoplanet? 05:00
We may bioengineer a species of humans with: multiple stocky legs and ultra-dense powerful muscles who can handle higher gravity; rapid genetic repair for mutations caused by stellar flares; ability to tolerate types and levels of gases that so far would make us sick. Our descendants may do away with human space travel altogether, instead sending raw biological materials and DNA to create humans on arrival, tailored to the specific planet conditions.
It is my dream to find all of the “Earths next door” and to oversee the space telescopes that will give us the basics so we know what level of geoengineering we should plan for. I’ll then pass the baton on to the next generations who will have to be both clever enough to develop interstellar propulsion and terraforming technology and brave enough to make the journey in whatever form.

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