The Southwest Research Institute has discovered that the solar systems may have lost a giant gas planet several million years ago.
Astronomer David Nesvorny managed to learn some secrets of the past of the solar system by looking at the Kuiper belt and the craters on the Earth's moon. He discovered a "dynamic instability" that may suggest a planet had once existed 600 million years ago between Mars and Jupiter.
There were several alternative scenarios to explain this instability, however, each held flaws that couldn't be solved through the application of the current solar system. Therefore, another giant planet of a size like Uranus or Neptune may help solve these flaws. By adding this new mass, the simulations of the solar system during that time period actually adds up.
“The possibility that the solar system had more than four giant planets initially, and ejected some, appears to be conceivable in view of the recent discovery of a large number of free-floating planets in interstellar space, indicating the planet ejection process could be a common occurrence,” Nesvorny said.
If you have any idea of the location of this theoretical, anonymous planet, feel free to contact the Southwest Research institute.