Have any Earth-based astronauts ever set foot on Mercury? No, Earth's spacecraft have visited Mercury, but no person has ever gone into orbit around Mercury, let alone trod on its surface. Mercury's equatorial surface temperature climbs to 700 Kelvin during the day (427 degrees C). At night it drops to 300 Kelvin (224 degrees C). This is much too hot for human comfort or survival.
Mercury is also extremely small and dense, being only 3% as massive as Earth while having a radius about 33% that of Earth's. With an average density of 495 kg/m3, it is about 18 times more dense than water and would need to be housed in something equivalent to a small car to provide sufficient mass for a landing.
The first object to orbit both planets was the Union Jack launched in 2003 by the United Kingdom. In 2008, the Soviet Union launched Mariner 10, which became the first object to orbit both Mars and Mercury.
However, because the surface tension of mercury is only 7 times that of water, it is implausible that a human could walk or run on mercury without breaking the surface tension (unless it is possible to devise some snow-shoe like contraption to increase the lift provided by surface tension). A small amount of dust may be able to settle on the skin, but nothing more.
Mercury has been used in laboratory experiments as a substrate upon which bacteria can grow. It has been demonstrated that certain strains of bacteria are capable of growing in medium containing concentrations of mercury higher than those tolerated by most other organisms. However, these studies did not involve exposure for periods longer than several hours at a time. Long-term exposure to low levels of mercury may have other effects beyond those observed in laboratory experiments.
In conclusion, humans can walk on mercury, but only for a few hours at a time and at very low concentrations. Anything more prolonged or intense might cause problems for the lungs. Mercury is also toxic to the kidneys, so prolonged exposure to low levels of this metal might cause them damage as well.
The only way to be sure whether you are not going to hurt yourself or others is to do careful research before you start any project.
Mercury has a density (g/cm3) of 13.5, while the human body (65-80% water) has a density of roughly 1.0. The lower density object would float, or at the very least not sink (remain buoyant), on top of the greater density substance. Walking on liquid mercury, as we know it, would be nearly impossible. However, there are several materials that are less dense than mercury and also more soluble than mercury. If someone were to wear shoes made of these materials they could potentially walk on hot liquid mercury without being injured by its surface tension.
However, such material pairs are rarely found in nature. Phosphorus is the only metal that is less dense than mercury and more soluble than mercury. It is also the only metal that is combustible under normal conditions. By combining phosphorus with other elements - such as arsenic, antimony, and sulfur - one can produce substances that are less dense than mercury but more toxic. In fact, elemental phosphorus is so reactive that even in powder form it will burn if exposed to air for long enough!
The combination of arsenic and phosphorus produces arsine, which is less dense than mercury but still more dense than air. Therefore, arsenic-based compounds are usually used in experiments where it is necessary to float something lighter than air but not as light as mercury.
Antimony combined with phosphorus produces antimony phosphide, which is less dense than mercury but more dense than air.
The whole Mercury Seven crew finally traveled into space. From May 1961 to May 1963, they piloted the six spaceflights of the Mercury program with an astronaut on board, and members of the group flew on all of NASA's human spaceflight missions of the twentieth century—Mercury, Gemini, Apollo, and the Space Shuttle.
They were: John Glenn, Navy test pilot; Alan Shepard, Marine Corps fighter pilot; Gus Grissom, Air Force colonel; Roger Chaffee, Army captain; and Walter Schirra, Naval officer. Glenn was the first American to orbit the Earth.
All of them except for Chaffee died in or as a result of their activities. He was lost in an aircraft crash after completing his third flight.
Chaffee is also one of only seven people to have flown on each type of manned spacecraft used by NASA (except for one vehicle that still exists). The others are Scott Kelly, Steve Rogers, Yuri Gidzenko, Victor Klassov, Andrey Borisenko, and Thomas Pesquet.
Glenn became the first person to orbit the Earth twice when he returned to space on America's greatest hero, John Glenn. They spent about five hours in orbit before returning to Earth.
And now let's see how many you can answer correctly...
197,374,706 miles Mercury and Earth are now separated by 197,374,706 kilometers, or 1.319368 astronomical units. Light takes 10 minutes and 58.3712 seconds to get from Mercury to us.
This value has been known since 1873 but it's still being discovered how accurate it is. The last major improvement was in 2014 when NASA improved the estimate by about 100 meters. The next step is for another mission to be launched at Mercury next year.
The mean distance between Mercury and the Sun is 47,904 miles or 79,904 km. At this distance, Mercury loses 790,000 acres of land every day due to radiation exposure. Its average surface temperature is -173 degrees F.
These values may change over time as more data becomes available.