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Published: 2015-02-18 07:10:00
Updated: 2015-02-19 09:04:26
Posted February 18, 2015
Updated February 19, 2015
By Tony Rice
A cold front arriving Wednesday will bring another blast of arctic air to the area with record low temperatures anticipated Thursday and Friday in the Triangle. However it was the very Mars-like forecast high temperatures that caught my eye.
Comparing the temperatures recorded by the Mars Curiosity rover last week to this week's forecast, the rover will likely see warmer weather than we will here in central North Carolina Thursday and Friday. Highs in the Gale Crater region where Curiosity is operating have reached the mid 30s to low 40s in recent days while temperatures at RDU are expected to stay well below freezing with highs of 17º F on Thursday and 24º on Friday.
Mars' atmosphere is very different from Earth’s. It is 100 times thinner and its carbon dioxide composition is flipped (Mars: 95 percent, Earth: 0.04 percent). That greater distance from the sun means less energy makes it to Mars, and the thinner atmosphere allows less energy to be retained.
Mars sees more extreme temperature fluctuations, even over the course of just one day.
Much of Mars' heat is lost to space each night but some of it goes along with the thermal tides. As the sun heats the day side of Mars, air expands upward creating an atmospheric bulge. That bulge travels from east to west with the sun as the planet rotates. The Curiosity rover has measured this cycle each Martian day since it landed in 2012.
Back here on Earth, our forecast also includes the possibility of some snow showers triggered by the arriving cold front Wednesday. Mars also has snowfall, but it consists of frozen carbon dioxide rather than frozen water. The Mars Reconnaissance Orbiter regularly reports the movements of dry-ice clouds during winter months. We think of snowflakes as being very tiny here on Earth but if you have ever looked closely at one on dark clothing, you can even make out the crystalline structure with your naked eye. You will not be doing that on Mars where data suggests that dry-ice snowfall there is more like a frozen fog with flakes the size of red blood cells. The average air pressure increases during summer months as the polar ice caps shrink, and that carbon dioxide returns to the atmosphere.
The ground on Mars does not do a very good job of retaining heat either. REMS data show that temperatures of the rock beneath the rover rise well above freezing – readings have been around 45º F in recent days – but fall to around -100º F, several degrees below the low air temperature.
We’ve been studying the Mars climate and comparing it to our own since observers in the 1700s first noted the polar ice caps there. Rudimentary measurements were made in the 1960s by the Mariner probes during fly-bys. The Viking landers took more accurate temperature and wind readings from a meteorology boom extending out from one of the lander legs. Study continues with the Mars Exploration Rovers (Spirit and Opportunity) and most recently the Curiosity Rover and its Rover Environmental Monitoring Station (REMS) instrument.
For the latest weather reports from the Mars rover Curiosity, you can follow @MarsWXReport on Twitter.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.