Scientists have determined that a patch of underground water over half a mile beneath the Earth's surface not only has a high salt concentration, but is also old enough to have been around during the time of dinosaurs.

Scientists lead by Ward Sanford discovered the ancient body of water, which is estimated to be about twice as salty as modern seawater and at least 100 million years old, according to Science Daily. The water was preserved due to the impact of a comet or meteorite 35 million years ago that formed the Chesapeake Bay. Ward explains how that massive impact helped preserve the sample of seawater as it was, and how it helps paint a more complete picture of ancient seas for scientists:

"Previous evidence for temperature and salinity levels of geologic-era oceans around the globe have been estimated indirectly from various types of evidence in deep sediment cores...In contrast, our study identifies ancient seawater that remains in place in its geologic setting, enabling us to provide a direct estimate of its age and salinity."

The ancient impact that made the modern day bay was so strong the impact broke up all the aquifers in the area and caused this unique sample to be preserved the way it was. Scientists estimate that the impact that created the Chesapeake was made by a comet or meteorite that blasted a hole in the ocean around 56 miles wide and created a tsunami that traveled all the way to the Blue Ridge Mountains 110 miles away. Jerad Bales, acting USGS Associate Director for Water, explains how rare this find is:

"We knew from previous observations that there is deep groundwater in quite a few areas in the Atlantic Coastal Plain around the Chesapeake Bay that have salinities higher than seawater...Various theories related to the crater impact have been developed to explain the origin of this high salinity. But, up to this point, no one thought that this was North Atlantic Ocean water that had essentially been in place for about 100 million years."

Bales also explained how much of a scientific impact this find could have for researchers:

"This study gives us confidence that we are working directly with seawater that dates far back in Earth's history...The study also has heightened our understanding of the geologic context of the Chesapeake Bay region as it relates to improving our understanding of hydrology in the region."