Lesson 1 of 6 · A changing landscape and a longer year
A changing landscape and a longer year
10 minute lesson · 3 checks along the way
Your goal for this lessonSeparate daily weather, seasonal cycles, and long-term climate change on Mars.
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A world with several clocks
Mars has dusty plains, battered highlands, immense volcanic landscapes, and polar ice. Its familiar reddish appearance comes largely from iron-bearing material altered into oxidized minerals, but individual rocks and surfaces have many shades. Color depends on dust, lighting, camera filters, and processing. A darker patch is not automatically vegetation, water, or a different rock type. Start by asking what an image actually measures before naming its cause.
The daily clock is a , about 24 hours 39 minutes long. Mars completes a year in about 687 Earth days, or 668.6 sols. Those are different units for nearly the same interval, not two competing orbital periods. Mission teams may count sols from their own landing dates, so “sol 100” does not identify the same planetary date for two different rovers.
Opposite seasons, unequal lengths
Mars’s spin axis is tilted about 25 degrees away from the perpendicular to its orbital plane. When the northern hemisphere leans toward the Sun, northern days generally become longer and sunlight arrives more directly; the southern hemisphere has the opposite seasonal tendency. Latitude still matters. Conditions near the equator do not copy those at a pole, and daily temperature swings can be large within one season.
The orbit is noticeably elliptical, adding another influence. Southern summer occurs near the part of the orbit closer to the Sun; southern winter occurs farther away. Orbital speed also changes, so the four seasons do not last equal numbers of sols. A calendar label therefore needs a hemisphere and a position within the Martian year. Distance alone cannot explain why the two hemispheres have opposite seasons simultaneously.
Check 1 of 3
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Ice exchanges material with the air
The polar regions contain water ice, while seasonal carbon-dioxide frost accumulates and disappears as temperatures change. Carbon dioxide depositing from gas into frost removes material from the atmosphere; returns it. This exchange helps produce the annual pressure cycle measured by Mars Science Laboratory Curiosity. Local elevation, weather, and time of day also affect a pressure reading. One number is not a planet-wide climate history.
The Hope Mars Mission image gives a broad view of the disk and its hazy limb, but its processed colors are not a pressure gauge. To investigate seasonal change, scientists compare observations with dates, locations, instrument settings, and uncertainties recorded. Repeated coverage can show patterns that an attractive single view cannot establish. Dust moving through the atmosphere can also change how clearly the surface appears.
Mars from Hope’s EXI observations, processed by Kevin M. Gill using the f635, f546, and f437 filter channels. The global view connects surface geography with the appearance of the limb; it is not a pressure map.
Look closely
Can this one processed view establish how atmospheric pressure changes through a Martian year?
See what to notice
No. It shows a particular view of the planet and its limb. A seasonal pressure claim requires repeated calibrated measurements with timing and location documented; picture color and visible haze alone do not supply pressure.
Check 2 of 3
10 pointsUse the reading above. You can try again without losing points.
Work through a decision
Work the evidence: cycle or trend?
Consider invented measurements at one fixed station and local time: 650 pascals early in a year, 780 later, and 660 at the same seasonal point the following year. The first increase is 130 pascals, or 20 percent of 650. That calculation describes the measured interval. It does not establish that pressure keeps increasing by 20 percent every year.
The return toward the starting value suggests a seasonal cycle worth testing. Compare several years at matching seasons and account for measurement uncertainty before proposing a long-term trend. Moving the station uphill between readings would introduce another explanation. Your next useful observation is a controlled repeat, not another percentage extrapolation. Mars changes on daily, annual, and geological timescales, and each claim needs observations spanning the relevant clock.
Check 3 of 3
10 pointsUse the reading above. You can try again without losing points.
Put it together
Your lesson progress
Each check connects to a part of the story. Complete all 3 to earn your 25-point lesson bonus.
Go to the source
Explore the evidence behind this lesson. These optional readings and videos open in a new tab.
- Read: NASA GISS: technical notes on Mars timeMean sol and tropical year; distinguish Earth days from sols.
- Read: NASA: two Martian years of seasonal cyclesMeasured pressure, temperature, and water-vapor cycles at Gale Crater.
- Read: ESA: seasons on other planetsTilt and orbital distance contribute differently to seasons.