Laser spectroscopy technology enables non-invasive chemical analysis of preserved Charles Darwin specimens, improving long-term preservation of museum collections
Researchers have performed a detailed analysis of original specimens collected by Charles Darwin on his voyage on the HMS Beagle to the Galapagos Islands (1831-1836), using a method that does not require opening centuries-old jars.
In a significant move to preserve museum collections, the team examined the contents of preservation liquids while the containers remained sealed, avoiding any risk to the unique material within.
Examination of 46 historical samples
The study focused on 46 historical specimens housed at the Natural History Museum in London. The collection included mammals, reptiles, fish, jellyfish and crustaceans collected by Darwin and other naturalists during the voyage.
The results showed that preservation methods varied depending on both the type of organism and the period of storage. Mammals and reptiles were typically fixed in formalin before being transferred to ethanol for long-term storage. Invertebrates, on the other hand, were sometimes preserved in formalin, buffer solutions, or mixtures that included additives such as glycerol.
Successful identification in 80% of cases
In testing, the technology successfully identified the preservation liquids in about 80 percent of the samples, with partial identification in another 15 percent. In addition to analyzing the liquids, the method also revealed whether the jars were made of glass or plastic, offering further clues about changes in preservation practices over time.
Portable laser technique
The researchers used a portable laser spectroscopy method called Spatially Offset Raman Spectroscopy (SORS) to penetrate through the glass and identify the chemical composition of the preservation fluids.
SORS performs chemical analysis by shining laser light into a container and examining the changes in wavelength that occur when the light is reflected. These changes indicate the presence of different chemical components within it.
SORS, originally developed at STFC's Central Laser Facility, is the same technique used in airport scanners around the world by Agilent Technologies.
Dr. Sarah Muska from the facility said: “Until now, understanding the chemical composition of the preservation fluid in each jar required opening them, which can cause evaporation, contamination and expose the samples to environmental damage. This technique allows us to track and handle these valuable samples without destroying them.”
Impact on museums around the world
More than 100 million liquid-preserved specimens are stored in museums around the world. For curators, knowing the exact composition of the preservation fluids is essential to monitoring the condition of the specimens.
The ability to analyze the chemical composition of preservation fluids non-invasively offers collection custodians and curators a new tool for monitoring the health of collections and intervening before problems arise.
Changing the study of natural history
Ren Montgomery, a research technician at the Natural History Museum, says: “As part of the NHM Unlocked project here at the museum, we can analyse jars containing specimens without opening them and compromising their integrity (“damaging” or “destroying” them). This work is the next step in demonstrating the museum’s commitment to transforming natural history research.”
She added: "Analyzing the storage conditions of valuable specimens and understanding the fluid in which they are preserved could have huge implications for how we handle collections and preserve them for future research for years to come."
The study was published in the journal ACS Omega. On January 13, 2026.
About the technology: SORS technology represents a breakthrough in the preservation of museum collections, allowing researchers to obtain critical information about the condition of historical specimens without compromising their integrity. The method is expected to find widespread application in museums around the world in the coming years.
More of the topic in Hayadan:
One response
The title was worded as "Scientists Solve 200-Year-Old Museum Mystery: What Do Darwin's Jars Contain?" But I was left with an accompanying mystery. Charles Darwin's voyage on the Beagle to the Galapagos Islands, during which he collected specimens, took place in 1831-1836. Parkesine, the first (semi-synthetic) plastic, was invented thirty years after Darwin's voyage, in 1862 by another Englishman – Alexander Parkes. At the earliest, in 1907, the American Leo Hendrik Baekeland invented Bakelite, the first synthetic plastic not based on natural materials, that is, after Darwin's death (April 19, 1882).
The article shows that "in addition to analyzing the fluids, the method also revealed whether the jars were made of glass or plastic." It is clear, then, that Darwin's initial preservation of the specimens he collected was not done in plastic jars. It is possible that in the last decade of his life, or more likely, after Darwin's death, the specimens were transferred from glass jars to plastic jars (the patent for the first plastic injection machine was registered in 1872). If this is the case, then there is 'no way' that "researchers have performed a detailed analysis of original specimens collected by Charles Darwin on his journey...".
From now on, say "original samples" – no. Second-hand samples – maybe.