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. We find a lake of liquid water filling a small crater close to one of the dry river channels.

Short answer

Surprising due to Mars' current environment, yet not implausible near ancient river channels with briny conditions.

Step-by-step solution

Understand Martian Environment

Mars is known for its cold and dry environment, with temperatures significantly below freezing for much of its surface. The thin atmosphere is mostly carbon dioxide and exerts very low pressure, making it difficult for liquid water to exist on the surface without quickly evaporating or freezing.

Evaluate Possibility of Liquid Water

Recent observations have suggested the possibility of liquid water in certain conditions on Mars, especially briny (salty) water, which has a lower freezing point. However, a lake of liquid water would be surprising due to the typically low temperatures and low atmospheric pressure.

Consider Historical Evidence

Mars has ancient features resembling dried-up riverbeds and lakebeds, indicating that liquid water existed in the past when Mars had a thicker atmosphere and possibly a warmer climate. Finding water near these areas could suggest that there are isolated pockets where liquid water could remain stable under current conditions, potentially underground or mixed with salts.

Conclusion Based on Current Understanding

Given the current understanding of Mars, finding a lake of liquid water on the surface would be considered surprising due to the existent environmental challenges. However, finding pockets of water mixed with salts in places connected to ancient water systems may be plausible.

Key concepts

Martian Environment

The Martian environment is quite harsh compared to Earth's, shaping our understanding of what might be plausible from a scientific standpoint. Mars has a cold, arid landscape with an average temperature of about -80 degrees Fahrenheit (-62 degrees Celsius), plummeting far lower during nighttime and in the winter. These frigid temperatures mean that any water on the surface could easily freeze.

The planet's atmosphere plays a crucial role in its environment, as it is extremely thin, composed mainly of carbon dioxide, and exerts only about 1% of Earth's atmospheric pressure. This low pressure combined with the cold makes it very challenging for liquid water to exist on the surface—it would either freeze or evaporate very quickly in most circumstances.

Though extremely dry by Earth standards, Mars is not devoid of weather. Dust storms are frequent and can cover the planet, contributing to its reddish hue. There are polar ice caps, which consist of water and dry ice, highlighting just how prevalent freezing temperatures are across the Martian surface.

Liquid Water on Mars

While finding liquid water on Mars would be extraordinary due to its climate and atmospheric conditions, scientists continue to investigate this possibility. Recent data collected from various Mars missions have pointed to some exciting potential evidence in favor of liquid water existing, albeit under specific conditions.

One theory involves the presence of briny, or salty, water. Salts can lower the freezing point of water, allowing it to remain liquid at temperatures where pure water would freeze. Researchers have observed features called recurring slope lineae (RSL), which are thought to be seasonal flows of water, possibly brine, that could seep down slopes during warmer months.

Furthermore, radar detections have hinted at possible subsurface lakes buried beneath the Martian ice near the South Pole. These underground lakes might remain liquid due to geothermal warmth from the planet's interior or high concentrations of salts, which keep water from freezing despite the polar conditions.

Ancient Martian Water Systems

Mars presents a landscape packed with clues about its watery past through features like dry river channels, ancient lakebeds, and delta formations. These geological structures suggest that Mars once had liquid water flowing on its surface, potentially billions of years ago, when its atmosphere was thicker and the climate was more temperate.

Studying these ancient Martian water systems provides insights into Mars' past climate and its potential to have supported life. Scientists speculate that ancient water systems could have connected vast lakes or even oceans, creating a habitable environment over parts of the planet.

Ancient water systems may hold secrets about the possibility of life on Mars, as liquid water is a key requirement for life as we know it. The existence and influence of these systems have shaped how scientists look for signs of past life, such as microbial fossils, or how they plan future missions aimed at uncovering more about Mars' history and its capacity to support life.