Experts long theorized that groundwater provided the salt necessary to keep Don Juan Pond in Antarctica from freezing. New research, however, finds they were mistaken and may give clues to how ponds formed on Mars.<\/p>\n
The pond was named after the two helicopter pilots who discovered it – Don Roe and John Hickey – and has long been the center of scientific debate.<\/p>\n
\u201cForty years of literature says groundwater is the cause,\u201d said James Dickson, data analyst at Brown University. \u201cBut it never hurts to triple check.\u201d<\/p>\n
Dickson and a team of researchers used time-lapse photography to study the pond after initial observations pointed to a possible alternative cause to its saltiness.<\/p>\n
\u201cWe weren\u2019t studying Don Juan Pond in the first place,\u201d said Dickson. \u201cWe saw water tracks around the pond and decided to take a look. We weren\u2019t sure what to expect.\u201d<\/p>\n
So they set up digital cameras to take photos of the pond every five minutes and meteorological stations near the floor of Don Juan Pond that measured relative humidity.<\/p>\n
\u201cThe cameras work really well. There\u2019s 24 hours of sunlight down there, so the solar packs keep charging,\u201d said Dickson.<\/p>\n
Cameras at the site captured 290 images a day over two months for a total of 16,000 images. The images provided the necessary proof to confirm that Don Juan Pond gets its salt from precipitation, not groundwater.<\/p>\n
\u201cMoisture comes from the ocean and it moves inland as snow,\u201d said Dickson. \u201cThe snow falls and it deposits salt on the surface.\u201d<\/p>\n
Dickson said that when humidity fronts move in, surface salt near the pond absorbs that humidity as part of a process called deliquescence. The same process is used advantageously by transportation managers who apply salt to icy roads. The salty water droplets that result make their way down sloping land into Don Juan Pond.<\/p>\n
\u201cThe deliquescence model is much more appropriate for explaining the pond\u2019s salt content,\u201d said Dickson.<\/p>\n
The approximate salt content of Don Juan Pond: 40 percent, which makes it 18 times saltier than seawater, Dickson said. That\u2019s twice as salty as the Dead Sea.<\/p>\n
In addition to disproving an aging hypothesis, the findings will aid the understanding of closed basin ponds on Mars.<\/p>\n
\u201cWe find dried-up closed basins everywhere on Mars,\u201d said Dickson.<\/p>\n
Mars is a very different place than Earth. It\u2019s very dry and its atmospheric density is much lower, Dickson said. Its average temperature is below the freezing point and its atmosphere is comprised of carbon dioxide. But the closed basins found there share an important feature with Don Juan Pond.<\/p>\n
\u201cWhat\u2019s important is the mineralogy,\u201d said Dickson. \u201cWe have some information on the basin bottoms showing that they have chlorides on their floors.\u201d<\/p>\n
Since the Martian ponds haven\u2019t been active in more than four billion years, Dickson said it wasn\u2019t possible to know exactly what types of ponds they were. The discovery that their floors contain chlorides is important, because 90 percent of Don Juan’s salinity is comprised of calcium chloride.<\/p>\n
\u201cIt\u2019s very close to what we\u2019re seeing at Don Juan Pond. If we dried it up, that would be all that\u2019s left,\u201d said Dickson. \u201cThere are examples on Mars, and we think we have a lead on what caused those ponds.\u201d<\/p>\n
Dickson was joined by James Head at Brown, Joseph Levy at the University of Texas and David Marchant at Boston University in the research, which was funded by the National Science Foundation.<\/p>\n
Top image:\u00a0A camera installed above Don Juan Pond in Antarctica\u2019s McMurdo Dry Valleys (Credit: Geological Sciences\/Brown University)<\/span><\/em><\/p>\n","protected":false},"excerpt":{"rendered":" Scientists uncover new evidence for why Don Juan Pond in Antarctica doesn’t freeze<\/p>\n","protected":false},"author":13,"featured_media":9088,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[60],"class_list":["post-9309","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-earth-atmosphere","tag-featured"],"remote_post_permalink":false,"remote_post_featured_image":false,"yoast_head":"\n