Researchers have developed a laser technique to examine the contents of Charles Darwin's original specimens from the Galápagos Islands without disturbing the nearly 200-year-old jars. The method, known as Spatially Offset Raman Spectroscopy, reveals the chemical makeup of preservation fluids inside sealed containers. This breakthrough aids museums in preserving delicate collections worldwide.
Charles Darwin collected specimens during his HMS Beagle voyage from 1831 to 1836, including samples from the Galápagos Islands that contributed to his theories on evolution. These items, now preserved in jars at the Natural History Museum in London, include mammals, reptiles, fish, jellyfish, and shrimp. A team of scientists recently studied 46 of these historic specimens using a non-invasive approach to avoid risks associated with opening the containers.
The technique employed is Spatially Offset Raman Spectroscopy (SORS), a portable laser method developed at the Science and Technology Facilities Council's Central Laser Facility and commercialized by Agilent Technologies. SORS directs laser light through the jar walls, analyzing scattered light to identify chemical signatures of the fluids inside. The analysis showed that preservation methods differed by organism type and era: mammals and reptiles were typically treated with formalin before storage in ethanol, while invertebrates used varied solutions including formalin, buffered mixtures, or additives like glycerol. The method accurately identified fluids in 80% of cases and provided partial results in 15%, also distinguishing glass from plastic containers.
This collaboration between the Science and Technology Facilities Council, the Natural History Museum, and Agilent Technologies offers a new tool for managing over 100 million liquid-preserved specimens in global museums. Dr. Sara Mosca from the STFC Central Laser Facility noted: "Until now, understanding what preservation fluid is in each jar meant opening them, which risks evaporation, contamination, and exposing specimens to environmental damage. This technique allows us to monitor and care for these invaluable specimens without compromising their integrity."
Wren Montgomery, a research technician at the Natural History Museum, added: "As part of NHM Unlocked, here at the Museum we can analyse jars containing specimens without opening and disturbing their integrity. This work is the next step in demonstrating the Museum's commitment to transforming the study of natural history. Analyzing the storage conditions of precious specimens, and understanding the fluid in which they are kept, could have huge implications for how we care for collections and preserve them for future research for years to come."
The findings were published in ACS Omega on January 13, 2026.