Phys.org's How sulfur helped make Earth habitable before the rise of oxygen says
Mapping the bonds and vibrational modes of molecules containing sulfur isotopes is helping to shed light on the chemical reactions that took place in Earth's atmosphere during the Archean era, before the atmosphere became oxygenated about 2.5 billion years ago.
The sulfur in the Archean Earth's atmosphere was emitted by volcanic activity, and through a process called mass independent fractionation, sulfur's various isotopes... became enriched in a manner that does not correlate with their mass.
It links to Computational analysis of vibrational modes in tetra-sulfur using dimensionally reduced potential energy surface and says that this paper
...explores some of the molecular bonds of a sulfur-4 (S4) molecule, and how these bonds affect the vibrational modes of the molecule, which in turn may influence the mass independent fractionation process.
Question: If the formation of tetra-sulfur is expected to be an important aspect of atmospheric chemistry in Earth's past, why is there so little experimental information on this molecule? Is it profoundly difficult to make, or to measure? Pardon the simple language, but What is tetrasulfur like? Why is there so little experimental information about it?
Wikipedia says only:
S4 has been detected in the vapour phase, but it has not been well characterized. Diverse structures (e.g. chains, branched chains and rings) have been proposed. Theoretical calculations suggest that S4 adopts a cyclic structure.