Jens Martin Knudsen (12 October 1930 – 17 February 2005) was a Danish astrophysicist. During his scientific career Knudsen authored or co-authored more than 100 scientific articles, and was a longtime advisor to NASA. Early years Knudsen was born in Haurum near Aarhus, Denmark. Knudsen was son of Haurum's grocers and grew up at the grocer's house together with his three brothers of whom Knudsen was the oldest. All of the brothers ended up becoming physicists. Physics He was originally educated as a school teacher, but in 1962 got his degree in physics and mathematics from the University of Copenhagen. Immediately after his degree, Knudsen received a job invitation to MIT where he spent the next two years as a guest teacher. During 1966-1967 he taught physics at Middle East Technical University in Ankara Turkey. From 1970 to 1973, he worked for UNESCO as a teacher of mathematics in Turkey and later in Brazil. In Universidade de Brasília Knudsen worked with Mössbauer spectroscopy. There in Brazil Knudsen got a direct opportunity to compare the color of Mars in the night sky with the color of the local terrain. It made him wonder if there were common reasons for the near-matched color. After Knudsen returned to Denmark, he concentrated his studies on meteorites, especially iron-rich meteorites where Mössbauer spectroscopy is especially effective. In 1990 Knudsen participated in a workshop called "The Environmental Model of Mars" in Hungary. One morning Knudsen had sat down at the morning table at the workshop and started an enthusiastic conversation about why Mars exploration is especially important with two people unknown to him; it turned out that they were Agustin Chicarro, who was ESA's Solar System Research Project Scientist and leading and George Scoon, the chief designer of ESA's orbiter probes. Both were thrilled about Knudsen's rhetoric and invited him to join a science team for a European probe to Mars. In one of these meetings, two people from JPL heard Knudsen talk about Mössbauer spectroscopy. Shortly after, they invited him to JPL to talk about Mössbauer spectroscopy in a future Mars mission. At that conference in California, Knudsen used the last five minutes and 45 seconds of his talk to present the idea of using an array of magnets with decreasing field strength as a sort of continuation on the magnetic experiment carried out on the Viking lander missions. This idea intrigued the conference and