Dark matter might not just making the universe more massive than it should be, it might also be making the universe more populous than it should be. Find out how.
One of the forces that lets scientists know that dark matter is out there is gravity. Scientists observed galaxies' gravitational interations with other galaxies, and noticed that they were behaving as though they had much more mass than was visible. Since dark matter exerts a gravitational pull, it has to be affected by gravity as well. Scientists believe that dark matter particles would orbit a galaxy's center of mass. As they orbited, they would pass through planets, and some particles would collide with the planets' atoms. Dark matter would build up inside the planet, adding to its mass and traveling toward its core. There they could hit other dark matter particles and annihilate, releasing energy and heating the planet.
Earth wouldn't be a candidate for the process, since it's trapped in a backwater region of the Milky Way, away from the center of the galaxy. Planets closer to the center could feel dark matter's heating effect, even if they didn't get energy from a nearby star. It's possible that this heat could even be enough to support life on these planets. Right now, though, the idea remains firmly an idea, since no current telescope could find a dark planet floating in space 26,000 light years away. Looks like the other planet would have to find earth.