The United States’ most important historical documents
may be spared from irreparable deterioration thanks to the
work of a team of NASA scientists working at the request of
the National Archives and Records Administration.

Scientists from NASA’s Langley Research Center, Hampton, Va.,
have confirmed the atmosphere enclosing the Declaration of
Independence, the U.S. Constitution and the Bill of Rights is
too moist.

In a report submitted to the National Institute of Standards
and Technology in Gaithersburg, Md. — the organization
contracted to provide encasements to the National Archives —
the team found there is nearly twice as much water vapor in
the atmosphere surrounding the documents as there should be.
As a result of the research, the National Archives will
replace the containers preserving the Charters of Freedom
over the next few months.

“The amount of water vapor or humidity in the encasements is
critical to their long-term preservation,” said Dr. Joel
Levine, the NASA scientist who managed the project and gave
the presentation. “Too much water vapor in a closed system
like these encasements has caused their glass to chemically
decompose, which could lead to eventual deterioration of the

“These documents form the basis of U.S. democracy, and it is
important to ‰erve them,” said Levine. “We’re happy we
were able to apply technology, originally developed by NASA
for atmospheric science, remote sensing, laser spectroscopy
and wind tunnel measurements, to ensure the future stability
of the Charters of Freedom.”

In the original encasements, deterioration of the glass
appeared as small surface cracks, crystals and droplets. This
deterioration would eventually cause the glass to become
opaque. Some humidity is necessary to keep the sheepskin
documents from becoming brittle: the preferred relative
humidity is less than 40 percent.

In the early 1950s, the documents, collectively known as the
Charters of Freedom, were sealed in specially prepared
containers. The cases were filled with humidified helium to
protect the documents. Many document-preservation experts
suspected the helium had leaked and allowed air to enter the
encasements, but the NASA team proved the cases remained
sealed in the original atmosphere.

“We were also surprised to discover the amount of carbon
dioxide in the encasements was nearly ten times higher than
levels found in Earth’s atmosphere,” said Levine.

NASA’s research group consisted of three independent teams:
two teams used non-invasive measurement techniques to study
the atmosphere through the glass encasement. The third team
used NASA instruments to determine the chemical composition
of extracted samples from each case. The teams, unaware of
the others’ findings and applying different methods, produced
very consistent results.

NASA examines different aspects of atmosphere as part of the
study of Earth System Science, an examination of the Earth in
an effort to better understand and protect it, while
bettering life on the planet.

More information about NASA’s Earth Science Enterprise is
available at: