Weather Blog

Think our weather's zany? Try Mars and its daily 123° swings

Think our weather's zany? Try Mars and its daily 123° swings
Mars rover Curiosity at the "Rocknest" site where the rover scooped up samples of windblown dust and sand. (Photo: NASA/JPL-Caltech/MSSS)

If the warm days of summer have you pining for some cooler weather, perhaps a trip to Mars is in order.

Sure, you'd need to build a spaceship, ask your boss for about 2 years off from work, and solve that whole "Mars has no oxygen, water, or Starbucks (yet)" issue but if you could get there, it would definitely be colder than a Seattle summer.

Tony Rice, a fellow weather blogger and volunteer with the NASA/JPL Solar System Ambassador program, maintains the @MarsWxReport Twitter feed, which gives the current weather once a Martian day (40 minutes longer than an Earth day) from the Mars rover Curiosity.

What we find is that Mars is a cold place that has some radical changes in temperature between day and night, when it gets really, really cold.

For example on Tuesday the high under sunny skies was 19F -- enough to add a bit of chilly relief from 85° weather without the instant frostbite. But once the sun went down, the temperature dropped to... -104, which is cold enough that even a traveler from Minnesota would probably don a jacket.

(To compare, Rice wrote that Monday was the 41-year anniversary of a Russian probe that landed on Venus and recorded a temperature of 878°F.)

What I found interesting is that Mars does have seasons somewhat similar to Earth since our planets have similar tilts on their axis (23.5 degrees for Earth; 25 for Mars) but their seasons last twice as long because their orbit takes 687 days to complete a year.

But despite these seasons, researchers have found that the temperature doesn't vary a whole lot through the year, at least where Curiosity is, which is inside Gale Crater about 5 degrees south of the Martian equator.

But one place where the seasons are noticed is in air pressure. Mars has an extremely thin atmosphere that registers around 8.5 hPa (hectoPascals, which is equal to a milibar). Standard Earth pressure is 1012 hPa and ranges from about 950-1040 through the year not counting mega storms that can get down into the low 900s. Which means Mars has about 1% the atmospheric pressure of Earth (another challenge you'd face heading up there.)

Rice says there are noted changes in the Martian pressure too -- ranging from 7.5 hPa to 9.5 hPa over a year, but they are much more gradual and due to changes in the the planet's carbon dioxide.

"Sol" is number of Martian days the rover has been on the planet

"That increased pressure comes from an increase in CO2 in the atmosphere driven by sublimation of the CO2 snow (aka dry ice) as the south pole receives more sunlight," he said. "The atmosphere ebbs and flows as much of 30% due to this. Any clouds seen by the rovers are likely these CO2 ice clouds (or dust). We have a water cycle on Earth, Mars has a CO2 cycle but skips the liquid step (pressures are too low to maintain a liquid state)."

Still, the changes are tiny enough that future Martian TV meteorologists can probably leave the "H" and "L" graphics back home. But that doesn't mean there wouldn't be anything to talk about.

"Curiosity itself is in a meteorologically interesting place, at the bottom of Gale Crater with a 5km mountain rising in the middle," Rice said. "We are seeing some interesting air flow patterns around that mountain, caused by heating and cooling of the crater walls and the mountain."

(And just think -- we wouldn't have to hurry to get the weathercast done to leave time for the traffic report!)

So next time the summer sun is beating down on you a bit, perhaps daydreaming that trip to the Red Planet can help make you feel a bit cooler.

That and a $3 ice cream cone should be quite refreshing (and a much shorter trip!)