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NASA discovers rocky Earth, but should we care?

Artist's conception of Kepler 10b

NASA’s primary planet searcher, the Kepler space observatory, produced one its most important findings the other day with the discovery of a world just 1.4 times the size and 4.6 times the mass of Earth – the smallest planet ever discovered outside of the solar system.

Launched in March 2009, the Kepler Mission was designed to search for Earth-like planets. While most planets observed to date have been several times larger and composed mostly of gas, this newly discovered planet – dubbed Kepler 10b – is made of a rock with a similar density to iron, suitable for a human to stand on. That is, if the surface temperature didn’t reach above 1,300 °C.

So, why is it significant if we couldn’t even live on it?

While the discovery of a rocky planet outside of the solar system may have been predictable, the fact that one had not been found still led to some difficulties when debating whether other habitable Earth-like planets existed. With astronomers now safely in the knowledge that they can find these rocky planets, the search for more can begin.

“Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come,” said Douglas Hudgins, a Kepler program scientist at NASA.

The discovery (although slightly disputed) of Gliese 581g last year and now the emergence of Kepler 10b means that planets have been discovered separately in the habitable zone (goldilocks zone) of a star and with a similar composition to that of Earth. Now, if we could find a planet that combined the two, things would start to get really interesting…

  • Jonny wrote: “Launched in March 2009, the Kepler Mission was designed to search for Earth-like planets. ”

    Sigh… no. Kepler was designed to look for planets as its primary mission. Any kind of planets. Among what it can find are Earth-SIZE planets. Kepler can’t really tell us if those planets are Earth-LIKE.

    • From NASA:

      “Kepler is a critical component in NASA’s efforts to find and study planets where Earth-like conditions may be present,” said Jon Morse, the Astrophysics Division director at NASA Headquarters in Washington.


      Its ultimate goal is, and must surely be, the discovery of planets like Earth that might be able to harbour life, and it is part of NASA’s mission to do just that. While I agree that it was designed to look for planets, the Kepler space observatory does possess the capabilities to deduce to an extent whether a planet is Earth-like in terms of its size, structure and/or composition.