Mars Reconnaissance Orbiter Samples Mars' Atmosphere And Finds A Surprise
June 13, 2013

Mars’ Atmosphere Is Constantly On The Move

Lee Rannals for - Your Universe Online

Researchers have discovered that temperatures in the Martian atmosphere regularly rise and fall twice a day.

According to the findings published in the journal Geophysical Research Letters, temperatures can swing by as much as 58 degrees Fahrenheit during this odd, twice-a-day pattern. The observations, made possible by NASA's Mars Reconnaissance Orbiter, show that the temperature drop takes place globally and year-round.

"We see a temperature maximum in the middle of the day, but we also see a temperature maximum a little after midnight," said Armin Kleinboehl of NASA's Jet Propulsion Laboratory in Pasadena, Calif., who is the lead author of a new report on these findings.

Global oscillations of wind, temperature and pressure are called atmospheric tides. These tides are driven by a variation in heating between day and night. On Mars, these atmospheric tides dominate short-term temperature variations throughout the atmosphere.

Tides that go up and down once a day are called "diurnal," while those that go up twice-a-day are known as "semi-diurnal." The semi-diurnal pattern on Mars was first observed in the 1970s, but the latest research shows it comes about more than just in dusty seasons.

"We were surprised to find this strong twice-a-day structure in the temperatures of the non-dusty Mars atmosphere," Kleinboehl said. "While the diurnal tide as a dominant temperature response to the day-night cycle of solar heating on Mars has been known for decades, the discovery of a persistent semi-diurnal response even outside of major dust storms was quite unexpected, and caused us to wonder what drove this response."

The semi-diurnal temperature pattern was unexpected, but it has been replicated in Mars climate models when the radiative effect of water-ice clouds are included.

"We think of Mars as a cold and dry world with little water, but there is actually more water vapor in the Martian atmosphere than in the upper layers of Earth's atmosphere," Kleinboehl said. "Water-ice clouds have been known to form in regions of cold temperatures, but the feedback of these clouds on the Mars temperature structure had not been appreciated. We know now that we will have to consider the cloud structure if we want to understand the Martian atmosphere. This is comparable to scientific studies concerning Earth's atmosphere, where we have to better understand clouds to estimate their influence on climate."

NASA's Curiosity rover reported data back in April that shows evidence that Mars' atmosphere has thinned over time. The study found that a heavier version of the Argon isotope has built up relative to a lighter one that existed in Mars' past. This discovery confirmed that about 95 percent of the planet's original atmosphere escaped into space.