# PTE SWT #8: Geological Evolution of the Red...

Summarize Written Text #8 - Level 1 - Feeds Writing + Reading

> Read the passage below and summarize it using one sentence. Type your response in the box at the bottom of the screen. You have 10 minutes to finish this task. Your response will be judged on the quality of your answer.

The primary driver of modern Martian geology is its atmosphere, which is mostly made of carbon dioxide, nitrogen, and argon. By Earth standards, the air is preposterously thin; air pressure atop Mount Everest is about 50 times higher than it is at the Martian surface. Despite the thin air, Martian breezes can gust up to 60 miles an hour, kicking up dust that fuels huge dust storms and massive fields of alien sand dunes. Once upon a time, though, wind and water flowed across the red planet. Robotic rovers have found clear evidence that billions of years ago, lakes and rivers of liquid water coursed across the red planet's surface. This means that at some point in the distant past, Mars's atmosphere was sufficiently dense and retained enough heat for water to remain liquid on the red planet's surface. Not so today: though water ice abounds under the Martian surface and in its polar ice caps, there are no large bodies of liquid water on the surface there today. Mars also lacks an active plate tectonic system, the geologic engine that drives our active Earth, and is also missing a planetary magnetic field. The absence of this protective barrier makes it easier for the sun's high-energy particles to strip away the red planet's atmosphere, which may help explain why Mars's atmosphere is now so thin. But in the ancient past, Mars seems to have had an inner dynamo powering a planet-wide magnetic field. What shut down the Martian dynamo? Scientists are still trying to figure out.

## Answer

Mars' geology, shaped by its thin atmosphere and lack of a magnetic field, contrasts its wetter ancient past when liquid water existed, and although evidence of flowing water remains, the absence of tectonic activity and atmospheric stripping has rendered the planet arid and inhospitable.

## Explanation

A successful summary identifies the transition from a once-habitable environment with liquid water to the current arid, thin-atmosphered state. It effectively synthesizes the role of the missing magnetic field and the absence of tectonic activity in shaping the planet's current condition.

## Hints

- Focus on the contrast between the planet's ancient past and its current state.
- Mention the factors that contributed to the loss of the atmosphere, such as the lack of a magnetic field.

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