John Hoffman (September 7, 1929 – February 3, 2021) was a

space scientist The following outline is provided as an overview and topical guide to space science: Space science encompasses all of the scientific disciplines that involve space exploration and study natural phenomena and physical bodies In common usage ...

who developed instruments for

Apollo 15 Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the United States' Apollo program and the fourth to Moon landing, land on the Moon. It was the first List of Apollo missions#Alphabetical mission types, J mission, with a ...

Apollo 16 Apollo 16 (April 1627, 1972) was the tenth crewed mission in the United States Apollo space program, administered by NASA, and the fifth and penultimate to land on the Moon. It was the second of Apollo's " J missions", with an extended sta ...

Apollo 17 Apollo 17 (December 7–19, 1972) was the final mission of NASA's Apollo program, the most recent time humans have set foot on the Moon or traveled beyond low Earth orbit. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on ...

, the Pioneer Venus project, and Giotto mission. He also designed the mass spectrometer for the Phoenix Mars Lander mission in May 2008. He was a professor of physics at the University of Texas at Dallas.

Education

Hoffman's father was a chemistry professor and his mother was a pianist. He learned to appreciate both science and music as a child, having played the clarinet and oboe. Hoffman received his bachelor's degree from St. Mary's College in Winona, Minnesota and continued his education at the

University of Minnesota The University of Minnesota, formally the University of Minnesota, Twin Cities, (UMN Twin Cities, the U of M, or Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Tw ...

under the mentorship of Professor A.O.C. Nier who pioneered the field of

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...

. His PhD dissertation was on the helium isotopic distribution in large iron meteorites.

Career

Hoffman spent 7 years at the U.S. Naval Research Laboratory in Washington, D.C., developing miniaturized mass spectrometers for space flight. These were flown on Aerobee and Javelin rockets. He joined the Graduate Research Center of the Southwest in 1966. His main interest was in the study of atmospheric/ionospheric composition and isotopic ratios for which he has developed instrument packages that have flown on many rockets and satellites.

Missions

He developed instruments for the Apollos 15, 16, and 17 lunar missions, the latter being part of the ALSEP surface package. The goal was to detect and determine the composition of the lunar atmosphere. There is an atmosphere on the Moon composed mainly of noble gases and hydrogen, but the pressure is lower than that in the best vacuum systems on Earth. His instrument flew on the

Pioneer Venus Multiprobe The Pioneer Venus Multiprobe, also known as Pioneer Venus 2 or Pioneer 13, was a spacecraft launched in 1978 to explore Venus as part of NASA's Pioneer program. This part of the mission included a spacecraft bus which was launched from Earth car ...

mission to Venus in 1978. Data was received throughout the descent of the probe to the surface. Carbon dioxide is the dominant gas in the atmosphere. A surprise discovery showed that for the two "sister" planets there is a two order of magnitude difference in the isotopic ratios (the ratio of the heavier to lighter forms of these gases) for hydrogen and argon than for those gases on Earth. These isotopic ratio differences have had large implications on models of the nature of the solar nebula and the formation of the present (secondary) atmospheres of the terrestrial planets. Hoffman was a member of the team who flew a mass spectrometer on the European Space Agency's ''Giotto'' mission to Halley's Comet in 1986. This instrument was developed by laboratories in four countries, three European and one at UT Dallas. It measured both the neutral and ionized constituents of the comet's coma. The coma contains, besides water vapor and H30 ions, an extended source of carbon monoxide. The atmosphere forms around a comet as it comes near the Sun and is heated by radiation from the Sun. Hoffman has also flown mass spectrometers on Earth orbiting satellites, Explorer 31, ISIS-II, AE-C, D, and E, and Wake Shield, plus numerous sounding rockets and stratospheric balloon flights. The first observations of the polar wind, ions flowing out from the atmosphere, were made by his ion mass spectrometer flown on the ISIS spacecraft in 1971. Hoffman was a co-investigator for the TEGA experiment that flew on the Mars Scout Phoenix mission that descended on Mars on May 25, 2008. The spacecraft will land in the far northern region of Mars, above the Arctic Circle in the area that the Mars Odyssey spacecraft has found evidence for water. An arm on the lander will dig a trench a meter deep in the surface of Mars to look for water ice and other water related substances (minerals). These will be scooped up and analyzed in a series of small furnaces. The effluents from the furnaces will be analyzed by the UT Dallas mass spectrometer to determine the presence of water and the mineralogical composition of soil samples. Isotopic ratios of the principal elements in the samples will be determined and compared to the isotopic ratios of the atmospheric gases that will be measured by the mass spectrometer when it is not analyzing samples from the TEGA furnaces.

References

{{DEFAULTSORT:Hoffman, John H. 2021 deaths Saint Mary's University of Minnesota alumni University of Texas at Dallas faculty University of Minnesota alumni 21st-century American physicists Mass spectrometrists 1929 births