No body is immune to impact by other bodies. Earth too is no stranger to body-play; Micro-micro meteorites accumulate by the giga-ton annually in the form of dust. Larger impact bodies such as the Chicxulub capable of delivering as much as 100 Teratons equivalent of TNT are also out there - but less frequent. As many as 132 meteorites found on Earth are identified as of Martian origin.
On October 17, 2013, NASA reported, based on analysis of argon in the Martian atmosphere by the Mars Curiosity rover, that certain meteorites found on Earth thought to be from Mars were actually from Mars.
Back in the 1960s/70s, Project Orion was a theoretical study on a nuclear pulse propelled space-ship. Several devices being flung out opposite to the desired direction of thrust. Each device imparting an absurdly humongous specific impulse on detonation.
What I therefore find myself wondering
How large would the impact have been on Mars to impart escape velocity to the rocks that eventually turned up on Earth?
Even given the turbulent environment on Mars, is there a possibility one of the impact craters - the source of an eventual martian meteorite, may be discovered by one of the missions presently on/under-way to Mars?
Is there a probability of discovering a Venerean meteorite here on Earth?
Could Chicxulub, or a comparable impact have imparted escape velocity, or larger to a rock such that it would eventually wind up on Mars, or Venus?