HELMHOLTZ PRIZE 2007 (award ceremony on 18.07.2007)

Dr. Göstar Klingelhöfer is honoured for his work "Entwicklung eines Miniaturisierten Mößbauer-Spektrometers (Development of a miniaturized Mössbauer spectrometer)".

2007 Prizewinner: Miniaturized Mössbauer Spectrometer

Prof. Dr. Ernst O. Göbel, Dr. Andreas Schlüter, Dr. Gert Hoffmann, Prof. Dr. Heinz Kluge, Dr. Göstar Klingelhöfer

Göstar Klingelhöfer was born in Gedern (Upper Hessia) in 1956. He studied physics at TU Darmstadt and was awarded with a doctoral degree there in 1990 at the Institute for Nuclear Physics. In 1999 he went to the University of Mainz and led the "Experimental Planetology" group which was dedicated, among other topics, to Mars exploration. After 2007 he took part in further projects to explore the Martian moon Phobos, to study comets within the scope of the ESA ROSETTA project and to explore specific locations on the Earth's Moon. He died in 2019.

The miniaturized Mössbauer spectrometer (MIMOS), which was developed and constructed under the leadership of Dr. Göstar Klingelhöfer by his teams at the University of Darmstadt and later at the University of Mainz, is a highly sensitive sensor which has been used to study the mineralogical composition of cave paintings in Brazil or of pigments in antique vases, for example. The MIMOS 2 spectrometer, which was built by Göstar Klingelhöfer and his colleagues in 2003, gained international recognition as the "minerology explorer" of the "Spirit" and "Opportunity" Mars rovers which landed on the surface of our neighbouring planet in January 2004 and searched for mineralogical traces of earlier water sources. Göstar Klingelhöfer received the 2007 Helmholtz Prize which included €20,000 for his paper "Entwicklung eines Miniaturisierten Mößbauer-Spektrometers (Development of a miniaturized Mössbauer spectrometer)".

MIMOS uses the Mössbauer effect for the spectrometry of atomic nuclei. For this, gamma radiation which was emitted by excited nuclei is resonantly absorbed by other nuclei and subsequently re-emitted. The atoms are arranged in crystal lattices. Due to this, emission and absorption occur recoil-free so that the emission and absorption lines display their extremely small natural linewidth.

Only if the emission wavelength and the absorption wavelength exactly correspond with each other (this can be achieved using the Doppler effect by slowly moving the gamma-ray source), will absorption with subsequent radiation occur which can be registered by a detector. Since the chemical bonds of the atoms change the excitation frequencies of the atomic nuclei slightly and in a characteristic way, one can distinguish different bonding states of specific atoms (such as iron) using Mössbauer spectroscopy. In the case of MIMOS, the radiation source is cobalt-57 nuclei. By means of electron capturing, these turn into excited, but stable iron-57 nuclei which subsequently emit gamma radiation.

Using Mössbauer spectroscopy of iron, MIMOS can determine the content of different iron minerals in a material or rock sample and characterize the sample in this way. As MIMOS is very handy in comparison to conventional Mössbauer spectrometers, weighs only 400 g and has an energy consumption of only 2 watts, it is appropriate for mobile applications on site. These advantages aroused the attention of NASA and ESA which then equipped their Mars missions with a space-suitable version of the MIMOS. The miniaturized Mössbauer spectrometer was able to determine specific iron compounds in Mars rock which can only have formed in humid environments. Hence, there must have been large quantities of water on Mars at one time.

Literature

G. Klingelhöfer: Mössbauer In Situ Studies of the Surface of Mars. Hyperfine Interactions 158, (2004) 117