That is late winter in the Northern Hemisphere of Mars, where the NASA Perseverance rover and the Ingenuity helicopter are exploring an area of the ancient river Delta that flowed into the Jezero cape billions of years ago.
Dust is the main feature of the red planet. Dust often announces the arrival of winter, but this planet is no stranger to snow, ice and frost. At Mars' poles, temperatures could drop to minus 123 degrees Celsius.
There are two types of snow on Mars. One is the kind we experience on Earth, made up of frozen water. A thin air mass on Mars and temperatures below zero degrees Celsius mean that traditional snow is subsiding, or moving directly from a solid body to an air mass, before touching the ground on Mars.
Another type of snow on Mars is CO2 snow (dried bamboo) and it can fall on the surface. Some centimeters of CO2 snow tend to fall on Mars in flat areas near the poles.
Sylvain Piqueux, a Mars scientist at NASA's Road Rewards lab in Pasadena, California, said: "The amount of snowfall was large enough for skiing to get through. However, if you want to ski, you have to go to a cape or cliff, where snow can accumulate on steep surfaces.
Up to now, no rotating moon or autonomous vehicle has seen snow falling on the red planet because the weather phenomenon only occurs at the poles below the cloud cover at night. Orbitrary cameras cannot see through the clouds and no robot can survive the freezing temperatures at the poles.
However, the Mars Climate Sounder device on the Mars MRO (Mars Reconnaissance Orbiter) Mars orbiter rotation ship can detect light that cannot be seen by the human eye. It has detected CO2 snow falling at the poles of Mars. The Phoenix rover, which made landfall on Mars in 2008, also used one of its laze devices to detect drying ice from Mars' north pole position about 1,609km.
Thanks to photographers, we know that snowflakes on Earth are unique and have six faces. Under the microscope, the snowflakes on Mars may look a little different.
Piqueux said: Since the dry ice has four symmeters, we know that the dry ice snow will have sides. Thanks to Mars Climate Sounder, we can know that these snowflakes will be smaller than the width of a human hair.
CO2 hail and mist also form on Mars and they may occur further away from the poles. The Odyssey spacecraft (which entered Mars' orbit in 2001) witnessed frost forming and turning into gas under the sunlight, while the Viking landing ship discovered ice on Mars in the 1970s.
At the end of winter, the ice layer accumulated during the season can melt and turn into gas, creating unique shapes that make NASA scientists think of Swiss cheese, spots of spots from dogs, fried eggs, spiders and other unusual shapes.
Throughout the winter in Jezero Census, the recent high temperature has been around minus 13 degrees Celsius, while the lowest has been around minus 84 degrees Celsius.
Meanwhile, at the Gale C study in the southern Hemisphere near Mars' equator, the autonomous vehicle Curiosity - which made landfall on Mars in 2012 - experienced the highest temperature of minus 15 degrees Celsius and the lowest of minus 76 degrees Celsius.
Mars' seasons tend to last longer because of the planet's equatorial trajectory around the sun, which means a year on Mars is 687 days, equivalent to nearly two years on Earth.
NASA scientists held a New Year's celebration on Mars on December 26, coinciding with the appearance of the spring festival in the Northern Hemisphere.
Scientists calculate Mars's year starting point from the northern axis of the red planet in 1955 - a point that starts at will. Calculating Mars years helps scientists track long-term observations, such as weather data collected by NASA's spacecraft over decades.
