Question

Suppose we were to make the following discoveries. (These are not real discoveries.) In light of your understanding of Mars, decide whether the discovery would be considered plausible or surprising. Explain clearly; because not all of these have definitive answers, your explanation is more important than your chosen answer. Photos from future orbiters show that new gullies have formed alongside some of the ones already seen in crater walls from orbiting spacecraft.

Short answer

Plausible, due to processes like dry ice sublimation.

Step-by-step solution

Understand Mars' Surface and Climate

Mars is known for having a very thin atmosphere and experiences cold temperatures, which are not typically conducive to the presence of liquid water that could cause gully formation. Gullies, often seen as evidence of liquid movements, would need a source of flowing material, such as water, for their formation.

Consider Possible Explanations for Gully Formation

Although Mars is mostly dry, recent studies suggest that transient briny water or dry ice processes, such as sublimation, could potentially form gullies. These are considered as plausible hypotheses for the gully formations observed.

Evaluate the Discovery Based on Current Knowledge

If new gullies are forming, it could suggest active geological or climatic processes, which are already known to occur on Mars to some extent, such as dry ice sublimation. However, it could also imply more unexpected factors, like subsurface liquid water, which would be surprising given the current scientific consensus.

Make a Reasoned Conclusion

Given that processes like dry ice sublimation could explain new gully formation, the discovery is plausible. However, if the gullies were found to be caused by factors not consistent with current theories, it would be surprising.

Key concepts

Mars gullies

Mars gullies are intriguing surface features, often resembling small valleys. They are typically found on steep slopes, such as crater walls and are thought to be formed by transient flows of liquid. These formations have sparked much interest because they resemble gullies formed by water on Earth. Most scientists initially thought that liquid water was the cause of these formations.

Recent research suggests that gullies on Mars might not necessarily involve liquid water. Instead, they could be formed by processes like sublimation, where ice turns directly into vapor without becoming liquid first. This is especially interesting because Mars has a colder climate and a thinner atmosphere, which affects the stability of water. Thus, traditional water-based erosion is less likely. This gives rise to alternative theories like flows generated by sublimating CO₂ ice, otherwise known as dry ice. Such processes could adequately explain the presence of gullies on this cold, distant planet.

Mars climate

The climate on Mars is distinctly different from Earth's. It is cold and arid, with an average surface temperature of about -80 degrees Fahrenheit (-62 degrees Celsius). Despite being a terrestrial planet like Earth, Mars only has about 1% of Earth's atmosphere. This thin atmosphere is primarily composed of carbon dioxide, with only trace amounts of water vapor.

Due to its thin atmosphere and greater distance from the sun, Mars experiences temperature extremes and brutal weather conditions. Wind is a significant factor, often causing dust storms that can envelop the entire planet. These harsh climates mean that liquid water is unstable on the surface under normal conditions, as it either freezes or evaporates quickly. Nonetheless, there are traces of water ice and occasional transient water droplets within the polar caps and underground layers, affecting the planet's surface processes.

liquid water on Mars

Liquid water is a precious commodity on Mars, largely absent from its surface due to the planet's harsh climate. The presence of liquid water would imply some regions temporarily escape Mars's extreme cold. Subsurface ice can occasionally melt due to geothermal heat or chemical interactions, leading to the formation of briny, salty water. This type of water remains liquid at lower temperatures, thanks to the dissolved salts.

Discoveries of potential sub-ice lakes and seemingly wet streaks on Martian slopes have fostered hope that Mars currently harbors liquid water in some form. However, direct evidence of stable liquid water remains elusive. Despite this, scenarios where liquid water could exist, such as near volcanic areas providing heat or minor atmospheric changes, keep scientists optimistic about the prospects of more profound discoveries tied to water on Mars.

Martian surface processes

Martian surface processes are governed by both geological and climatic factors. The surface of Mars is shaped by phenomena such as volcanic activity, impacts from meteors, and strong planetary winds. These processes continually alter the landscape, creating varied terrains from vast plains to towering volcanoes.

Sublimation plays a crucial role in shaping features on Mars, particularly with the seasonal melting of CO₂ ice caps, which in turn may drive weather patterns and surface changes. Wind erosion is another significant force, continuously redistributing surface materials and sculpting the terrain. Landslides and dust storms further impact the Martian surface, creating easily recognizable features and patterns.

• Volcanism: past eruptions have left a legacy of mountains and craters.
• Wind erosion: reshapes Martian dunes and sand formations.
• Sublimation: affects polar ice caps and contributes to seasonal changes.

Martian surface processes are complex and varied but provide exciting insights into the planet's ongoing geological activity and climatic phenomena.