This Day In History : July 21

1973 United States

The USSR launched Mars 4

In 1973, the USSR launched Mars 4, on a Proton SL-12/D-1-e booster. The Mars 4 reached Mars on 10 Feb 1974. Its intended mission was to be an orbiting station. Sadly, retro-rockets failed to fire, due to a flawed computer chip, and it flew past within only 2200-km of the planet. A limited series of pictures and data were returned, including the first detection of the nightside ionosphere. 

Also on This Day in History July 21

Discover what happened on July 21 with HISTORY's summaries of major events, anniversaries,
famous births and notable deaths.

Births on This Day, July 21
  • 1923 Rudolph A. Marcus

    Canadian-born American chemist, winner of the 1992 Nobel Prize for Chemistry for his work on the theory of electron-transfer reactions in chemical systems.

  • 1810 Henri-Victor Regnault

    French chemist and physicist noted for his work on the properties of gases.

  • 1620 Jean Picard

    French astronomer, cartographer and hydraulic engineer who is regarded as the founder of modern astronomy in France.

  • 1873 Howard Turner Barnes

    He was an American-Canadian physicist who specialized in calorimetry, electrolytes, ice formation and ice engineering.

  • 1881 George Frederick Dick

    American physician and pathologist who, with his wife, Gladys Henry Dick, isolated the hemolytic streptococcus that was the cause of, and developed an immunization to treat, the dangerous scarlet fever (1924).

Deaths on This Day, July 21
  • 1919 Magnus Gustaf Retzius

    Swedish anatomist and anthropologist best-known for his studies of the histology of the nervous system.

  • 1926 Washington Augustus Roebling

    American civil engineer under whose direction the Brooklyn Bridge, New York City, was completed in 1883.

  • 1998 Alan B. Shepard Jr.

    Alan Bartlett Shepard, Jr. was an American astronaut who was America's first man in space and one of only 12 humans who walked on the Moon.

  • 2004 Edward B. Lewis

    Edward Butts Lewis was an American geneticist, a corecipient of the 1995 Nobel Prize in Physiology or Medicine.

  • 1971 Yrjo Vaisala

    Yrjö Väisälä was a Finnish astronomer and physicist. His main contributions were in the field of optics. 


The first nuclear-powered cargo passenger ship, the NS Savannah is launched

NS Savannah was the first nuclear-powered merchant ship. She was built in the late 1950s at a cost of $46.9 million (including a $28.3 million nuclear reactor and fuel core) and launched on July 21, 1959. She was funded by United States government agencies. Savannah was a demonstration project for the potential use of nuclear energy.

The world's lowest temperature is recorded at Vostok Station, Antarctica at -128.6 degrees F

The world's lowest temperature was recorded at Vostok Station, Antarctica, on July 21, 1983. Vostok Station is a Russian research station located inland, near the South Pole. This record-setting temperature was measured at -128.6 degrees Fahrenheit (-89.2 degrees Celsius), making it the coldest natural temperature ever observed on Earth.  

Launch of Mercury 4 (Liberty Bell) with Grissom

Mercury-Redstone 4 was the second United States human spaceflight, on July 21, 1961. The suborbital Project Mercury flight was launched with a Mercury-Redstone Launch Vehicle, MRLV-8. The spacecraft, Mercury capsule #11, was nicknamed Liberty Bell 7. It was piloted by astronaut Virgil "Gus" Grissom.

World's strongest dog, 80-kg St Bernard, pulls 2909-kg load 27 m

The story of a St. Bernard pulling a 2909-kg load over 27 meters demonstrates their impressive pulling power and muscular strength. These dogs have a thick, dense coat that provides insulation against cold weather, which also adds to their robust appearance
Special day
Discover invention