NASA’s first weather report from Mars: It’s super cold

But how big are the raindrops?

The first weather report from Jezero Crater confirmed the expected subzero temperatures.
The first weather report from Jezero Crater confirmed the expected subzero temperatures.

A weather sensor onboard NASA’s Perseverance Rover measured a temperature of -4° below Fahrenheit when the system started recording the day after the rover touched down in Jezero Crater on the Red Planet.

And the weather changes fast. Within just 30 minutes that temperature dropped to -14° Fahrenheit.

Skies were pretty clear. The radiation and dust sensor showed Jezero was experiencing a cleaner atmosphere than Gale Crater around the same time, roughly 2,300 miles away.

Perseverance’s 12-pound weather station records dust levels and six atmospheric conditions – wind, relative humidity, air temperature, ground temperature, radiation and pressure every hour.

The pressure measurement is interesting compared to Earth’s dense atmosphere.

Our atmosphere puts about 14 pounds of pressure per inch on us every day, but on Mars, the atmosphere is much less. Pressure sensors measured only 7.2 millibars or less than 1% of the weight here on Earth.

What would that lighter air do to raindrops on Mars? Well, if it didn’t just snow carbon dioxide or dry ice we could expect to see much bigger drops.

Raindrops on Earth are made of water, but other worlds in our solar system have precipitation made of more unusual stuff.

The gravitational pull on Mars is so weak that raindrops would be about 18 millimeters wide or almost as big as a penny. In comparison, gravity’s stronger force keeps our planet’s largest raindrops to about 11 millimeters in diameter.

. (AGU)

Just imagine being pelted by quarter-sized methane or liquified natural gas. This is the reality on worlds like the moon of Titan which has an extremely weak gravitational pull.

So much for refreshing summer downpours elsewhere in the solar system.


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