The polar vortex-inspired cold wave pooling over the U.S. this week has broken temperature records left and right. More than once I’ve heard pink-cheeked TV meteorologists say it’s colder than Mars. Are they right?
Well, sort of. Naturally it depends on where and when you poke your thermometer. A summer day on the Martian equator can see the mercury rise to 70 degrees F (20 C). Wait a minute. That means Duluth’s colder than Mars seven months a year. Summertime highs at mid-latitudes are closer to 32 F (0 F), still much nicer than what Chicagoans will experience today.
Mars is considerably colder than Earth’s because the planet is on average about half again as far from the sun as Earth. If you stand farther from the wood stove, the heat is less intense. The same is true with planets whirling around a central sun.
Day-night temperature variations are more extreme than Earth’s because Mars’ atmosphere is exceedingly thin, less the 1% that of Earth. The atmosphere of Mars heats up quickly and reaches occasional pleasant-sounding highs, but when the sun goes down, the skimpy air can’t hold onto the heat. Temperatures plummet.
Remember that 70 degree high? At night the temperature at the same locale can dip to -100 F (-73 C). The average temperature planet-wide is around -70 F (-57 C).
Maybe the weather forecasters were referring to Gale Crater, home to the Curiosity Rover, when making their temperature comparisons. Although it’s almost winter there (solstice on Feb. 15), since the rover is near the equator the season isn’t nearly as extreme as at mid-latitudes. Indeed, the rover has recorded highs above freezing on more than half the days it’s spent on the planet. Temperatures there have been dropping as Martian fall slinks toward winter but are still relatively balmy.
As recently as Dec. 31, the rover recorded an afternoon high of -22 F (-30 C), very close to the -21 F high I experienced yesterday while taking pictures in Embarrass, Minn. Standing in the 25 mph wind to photograph a street scene, it not only felt colder but truly was colder than Gale Crater on New Year’s Eve.
While northern Minnesota temperatures dropped to around 30 below this morning, Curiosity bested us by a mile with a high of minus 76 F on Jan. 2. And that’s without the wind chill. Martian winds range from pleasant zephyrs to hair-ripping gales. While the average wind speed is around 20 mph, seasonal winds can whip off the poles at up to 250 mph (400 km/hr). While the thin air no doubt makes the wind chill factor not as intense as Earth’s, it’s still enough to regularly dust off the Opportunity rover’s solar panels and conjure up thousands of dust devils.
Like the weather here in the northern U.S., things have turned frigid of late in Gale Crater with highs around -76 F and nighttime lows of -193 F.
So we see, not surprisingly, that Martian temperatures are variable but generally much colder than Earth’s. If the weather-folk want to more accurately compare Mars and Earth weather, instead of cherry-picking favored times and locations, they should at least compare typical mid-latitude Martian winter highs and lows with the current winter highs and lows in U.S. mid-latitudes.
Duluth’s high and low temps Monday were -15 F and -28 F for an average of -21 F (-29 C). At a similar latitude on Mars the average air temperature in the winter months is around -115 F (-50 C), far colder than anything we’ll experience this week whatever the meteorologists might say.