Venus, which orbits every 225 Earth days, has circled the sun around 7.3 billion times, and Mars, with a period of 687 Earth days, has logged around 2.4 billion revolutions.

Stock illustration of all the solar system's planets. Mars, Venus, Jupiter, Saturn, Uranus and Neptune will be visible all at once this month.

Two probes — BepiColombo, headed to Mercury, and Solar Orbiter, en route to the sun — recently passed by Venus at nearly the same time, visiting Earth's sister planet within a day of each ...