July 24, 2015 | David F. Coppedge

You Wouldn't Want to Live on "Earth's Cousin"

Despite the hype about another Earth-like exoplanet, Kepler 452b would not be as habitable as Venus.

When the Kepler Space Telescope team announced the closest match to Earth yet seen, a planet named Kepler 452b, reporters went berserk with the “cousin” metaphor and other comparisons making it sound like a second home:

  • It may not be Earth’s exact twin, but it’s a pretty close cousin. (Space.com)
  • NASA’s Kepler Mission Discovers Bigger, Older Cousin to Earth. (Astrobiology Magazine)
  • Bigger, older cousin to Earth discovered: NASA’s Kepler mission confirms planet in ‘habitable zone’ around sun-like star. (Science Daily)
  • Earth 2.0‘ found in Nasa Kepler telescope haul. (BBC News)
  • Earth-like alien world looms into view through Kepler telescope. (New Scientist)
  • NASA discovers Earth-like planet orbiting ‘cousin‘ of Sun. (PhysOrg)
  • NASA spies Earth-sized exoplanet orbiting Sun-like star. Potentially rocky world spotted by Kepler spacecraft offers glimpse at Earth’s future. (Nature)
  • NASA spots most Earth-like planet yet. (Science Magazine)

Moving from out to far-out, Amanda Doyle on Astrobiology Magazine leaped off the deep end into speculation with this article, “Mini-Neptunes Might Host Life Under Right Conditions.” A long chain of what-if’s led her to imagination of life deep under crushing atmospheres of Neptune-size exoplanets located far from M-dwarf stars with their dangerous flares.

BM-Darwine-sm“While water is great for life, this could be tricky for supporting a biosphere, since high pressure ices can form at the bottom of the ocean and interrupt the carbon cycle on these planets,” explains Luger. “But we still have no idea how chemical cycling occurs on water worlds, so we can’t rule out life on these planets just yet.”

Reality Check

Only a few reporters put a “reality check” in the headline. Mike Wall at Space.com ventures to model “What it would be like to live on ‘Earth’s cousin’.” Being 60% wider and 5 times more massive, Kepler 452b would make you gain weight. You would be twice as heavy there, and the strain on muscles and bones could be like a hard workout all the time. But that’s not the only woe. The higher gravity might also create a dense atmosphere with a runaway greenhouse effect, leading to a scorching world like Venus. Although the planet’s star is similar to Earth’s, it might be more active, bathing the planet in radiation from flares, boiling away its oceans (if it has any).  Another article on Space.com contains an infographic about the planet’s parameters.

Elizabeth Tasker on The Conversation is more realistically blunt. “Why it is misleading to compare exoplanet Kepler-452b to Earth” begins her more empirically honest evaluation:

NASA’s announcement of the discovery of a new extrasolar planet has been met with a lot of excitement. But the truth is that it is impossible to judge whether it is similar to Earth with the few parameters we have – it might just as well resemble Venus, or something entirely different.

The planet, Kepler-452b, was detected by the Kepler telescope, which looks for small dips in a star’s brightness as planets pass across its surface. It is a method that measures the planet’s size, but not its mass. Conditions on Kepler-452b are therefore entirely estimated from just two data points: the planet’s size and the radiation it receives from its star.

From there, Tasker takes on the “habitable zone myth.” Kepler 452b may be within its star’s habitable zone – “a term that sounds excitingly promising for life, but is actually misleading.” Habitability is defined as a radius from a star where water could exist “on a suitable planet’s surface,” she notes, focusing on that word “suitable.” Many other factors have to be taken into account for a planet to qualify: mass, geology, plate tectonics, volcanic activity, crustal composition, and atmospheric composition to name a few. “Earth’s cousin” also seems to be alone, lacking a giant planet that could deliver water or protect it from impacts. “Conditions on a planet’s surface are dictated by a myriad of factors – including atmosphere, magnetic fields and planet interactions, which we currently have no way of measuring,” she ends. Exciting as the find is, knowing what conditions are really like there is “a problem we cannot yet tackle.” She would probably criticize this statement by a Kepler scientist as misleading: “It would feel a lot like home, from the standpoint of the sunshine that you would experience” (Space.com).

Not many reporters are asking why there are so few Earth-like candidates out there.

Why travel to Earth’s cousin when Earth’s twin is just next door? Yes, take your next vacation on Venus. Enjoy the balmy breezes of sulfuric acid next to the volcanic lavas while getting that perfect tan in 900° heat. Feel oneness with our sister planet as your tissues burn and melt into the planet’s surface. You are now Venus, too! Earthlings can look up at the evening star fondly in your memory. Aren’t Earth-like planets fun? Travel to them all as part of your bucket list. Each one makes a nice bucket to kick.


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  • John C says:

    So which is it? Earth’s cousin, Earth’s twin? If it is older, how can it be Earth 2.0? I long for the days when the average person learns to read critically.

  • rockyway says:

    “It may not be Earth’s exact twin, but it’s a pretty close cousin. (Space.com)

    – Almost everything from the media is laced with hype. Remember that these are the same people who claim that Darwinism isn’t a theory but a fact… and that there are no problems with evolution. These are the same folk who claim human beings are just animals, and that chimps should have the same rights as people. (etc. etc.) They play fast and loose with the truth, and apparently there’s nothing they won’t say.

    ”NASA spots most Earth-like planet yet. (Science Magazine)

    – This akin to looking over pebbles at the beach and exclaiming ”wow, look guys, this is the most human looking one yet.”

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