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The possibility — and importance — of finding water on other planets

Virtual ASX “Star Talk” features York University astronomer Paul Delaney
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In his talk, Delaney discussed the evidence for Mars having liquid water billions of years ago. SPENCER KI/THE VARSITY
In his talk, Delaney discussed the evidence for Mars having liquid water billions of years ago. SPENCER KI/THE VARSITY

People with a passion for science, whether they are in grade four or teaching at university, wonder whether there is life on other planets. Are we alone in the solar system, or even in the entire galaxy? 

On January 20, the Astronomy & Space Exploration Society (ASX) hosted an online “Star Talk,” where Paul Delaney, a professor from the Department of Physics and Astronomy at York University and Carswell Chair for the Public Understanding of Astronomy, talked about the possibility of finding water — and perhaps life — on other planets.

“Star Talk” is a regular feature of the ASX’s programming, often accompanied by a guided telescope observation of the night sky. This year, with the telescopes closed, the ASX has had to adapt to online programming. One of the ways the ASX is maintaining audience participation is with “livestream watch parties and StarTalk-themed trivia nights,” according to a statement to The Varsity from ASX president Julie Midroni.

“The major challenges we faced in adapting to COVID-19 have been with our symposium — by far our biggest event of the year,” Midroni added. To compensate for the lack of in-person interaction, this year, the ASX is extending its symposium from a single-day event to a three-day event, scheduled for February 15–17.

Why does water matter?

“Life on this planet simply could not exist in the absence of water,” said Delaney at the beginning of his talk. He added that, while we cannot totally rule out the possibility of life existing without water, all of our current biological understanding suggests that water is a key ingredient to the presence of life. Thus, by searching for water, we can maximize our chances of finding life.

Water is a chemical compound that is relatively common in the universe because it is made up of two of the most common elements in the universe: hydrogen and oxygen. Relative to the total mass of our planet, the amount of water on Earth is actually pretty small — but its presence has allowed life to flourish.

There are several existing and extinct sources of water in our astronomical neighbourhood, including Venus and the Moon. For a long time, the prevailing belief was that the Moon did not have water. Even to this day, many people, including myself, have been unaware of the Moon’s surprising amount of water, much of which is frozen at the poles. There are also some indications that Venus used to have an Earth-like atmosphere with a watery surface. Right now, however, it is too hot for liquid water to exist.

Mars and its ancient past

But by far the most exciting source of water is Mars. It is, as Delaney said, “the planet we just love to talk about.”

“Mars today is a very arid environment,” he said. However, there are ice deposits all over its surface, which raises the question of whether ice on this planet was once water. More recently, radar instruments have detected the presence of liquid water on Mars’ surface, albeit in a highly saline form too salty to support life. But the existence of liquid water is still a promising sign that Mars may have been habitable in the ancient past.

“In fact, Mars may have been more hospitable than Earth back four billion years ago,” said Delaney. When asked by an attendee why the ice on Mars has not been sampled yet to search for signs of life, Delaney said that sending a spacecraft to Mars is very expensive, which makes this mission hard to achieve.

Presently, Mars lacks a substantial atmosphere, making life impossible on its dusty surface. The loss of its water is thought to be tied to the loss of its atmosphere. 

As a small planet, Mars may have cooled quickly in the billions of years following its formation, which may have caused its liquid metal core to partially solidify. Without a rotating liquid metal core to produce a protective magnetic field around the planet, harsh solar winds may have stripped the planet of its atmosphere and, eventually, its water.