The mystery surrounding the twice-daily temperature changes on Mars may finally be solved. Researchers believe water-ice clouds may cause Martian temperatures to change dramatically over the course of a single day.
Unlike Earth, which sees mild temperature changes throughout the day but a major change between night and day, Mars' temperature changes twice a day. The temperature on Mars reaches its peak during the middle of the day and again just after midnight, according to Armin Kleinboehl, from NASA's Jet Propulsion Laboratory, in a report published in the journal Geophysical Research Letters.
If that happened on Earth on a hot summer day, imagine 90-degree heat at noon and again at midnight, and in-between those peaks, sharp drops in temperature. On Mars, the temperature can drop more than 58 degrees F within hours, according to NASA.
Using NASA's Mars Reconnaissance Orbiter and data collected by the Mars Climate Sounder, researchers were better able to understand the mystery surrounding Mars’ atmospheric tides. As NASA explains, atmospheric tides are similar to ocean tides. Changes in wind, temperature and atmospheric pressure vary slightly across Earth during the day and night. It was believed that Mars’ twice-a-day atmospheric tides, called “semi-diurnal” while a once-daily occurrence is called “diurnal,” occurred only during the dusty seasons. The behavior was first discovered in the 1970s, and researchers speculated it was due to the sun heating up dust in Mars’ atmosphere.
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The latest data proved the phenomenon occurred year-round on Mars, which meant the previous theory was incorrect. According to Kleinboehl, “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 answer lies in the water-ice clouds found in Mars’ atmosphere. The ice-clouds are common on Mars, usually six to 13 miles above its surface, and act as reflectors causing the spikes in temperature. The ice-clouds absorb infrared heat from the surface of Mars, which causes the atmosphere to heat up during the day.
Kleinboehl notes the Martian atmosphere has even more water vapor than Earth’s atmosphere and that understanding water-ice clouds, much like studying clouds on Earth, will lead to a better understanding of the Martian atmosphere and climate. Kleinboehl says, “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.”