Although no definitive life has been found in our solar system, scientists are still searching for evidence. For example, Mars may be smaller than the Earth, and farther away from the Sun than Earth, but some scientists believe the planet may have once had small organisms living on its surface. The latest probe, the rover Curiosity, tested the surface rock and soil in 2012 and 2013, hoping to prove that organic material is present on the planet and is actually from the planet, not contamination from meteorites or the rover itself. And scientists are also suggesting, based on living bacteria found in Antarctica’s Lake Vostok (12,100 feet [3,700 meters] deep), that the frozen satellites (moons) of the outer planets—such as Jupiter’s Europa and Neptune’s Triton—may harbor bacteria in or under their ice. In fact, some scientists believe that the pull of Jupiter causes Europa to have “tides,” allowing the ice to melt under the planetary ice coating and create a watery ocean that may harbor life.