Mars' halcyon times may have been fleeting

2014-04-13 22:14
(<a href=”http://www.shutterstock.com”>Shutterstock</a>)

(Shutterstock)

Multimedia   ·   User Galleries   ·   News in Pictures Send us your pictures  ·  Send us your stories

Paris - Cold and dry today, Mars was previously warm and wet but possibly only at intervals, a study published on Sunday suggests.

Scientists have long puzzled over what happened to the water, the precious stuff of life, on the red planet.

Unmanned spacecraft have sent home tantalising images of gouged canyons, valleys and sedimentary deltas, while landers have found hydrous rocks, all suggesting Mars at one time hosted hundreds of kilometres of rivers and lakes.

Today, though, Mars is too cold and the pressure of its carbon-dioxide atmosphere way too low for liquid H2O to exist. If you tried to pour water on its surface, it would simultaneously freeze and vaporise.

So when did Mars host liquid water? And what happened to it?

In a study published in the journal Nature Geoscience, planetary geologist Edwin Kite of the California Institute of Technology takes a new stab at the riddle.

Kite and his team measured craters, left on the Martian surface by asteroid collisions, to gain an idea of its past atmospheric pressure.

The principle behind their calculation is this: the thicker the atmosphere, the bigger the space rock has to be in order to survive the friction of contact with it.

Conversely, a thinner atmosphere means that smaller rocks are able to survive the descent and whack the surface.

Kite's team looked at 319 craters in Aeolis Dorsa, a 3.6-billion-year-old region that shows evidence of past rivers to get an indication.

Mystery of flowing water

They calculated that these craters were formed when Mars had atmospheric pressure of up to 0.9 bar.

This pressure is 150 times greater than that of today and intriguingly close to that of the water-rich Planet Earth at sea level.

The bad news, though, is that Mars is far more distant from the Sun than Earth and at that far-off time, our star was much less bright than now.

As a result, Mars would have required pressures of at least five bar for its surface to keep above the freezing point of water. It seems to have lacked a long-lasting thick atmosphere during its river period.

"If Mars did not have a stable multi-bar atmosphere at the time that the rivers were flowing - as suggested by our results - then a warm and wet CO2/H2O greenhouse is ruled out, and long-term average temperatures were most likely below freezing," said the study.

This throws up other possible explanations for the water, said Sanjoy Som of Nasa Ames Research Centre in a commentary published in the same journal.

One is that the water was high in acidity and salt content, giving it a lower freezing point and enabling it survive as a liquid in lower air pressure.

Another is that greenhouse gases from volcanic eruptions helped Mars, for a while, to have a denser atmosphere that enabled the water to flow.

Another possibility is "transient intervals" of denser atmosphere caused by the planet's tilt, said Som.

Like a child's top that is slightly off centre, Mars tilts slowly around its axis of spin.

It takes 120 000 years to complete one axial revolution, a timescale that leads to major changes in the amount of sunlight reaching its poles, whose water either froze to form ice-sheets or warmed to "reinflate" the atmosphere and form rivers that flowed at kinder times.

Read more on:    space
NEXT ON NEWS24X
SHARE:

Read News24’s Comments Policy

24.com publishes all comments posted on articles provided that they adhere to our Comments Policy. Should you wish to report a comment for editorial review, please do so by clicking the 'Report Comment' button to the right of each comment.

Comment on this story
0 comments
Add your comment
Comment 0 characters remaining
 

Inside News24

 
/News
 

This is what South Africans Googled in 2014!

Find out who and what South Africans were most curious about in 2014!

 
 

I love summer.24

This hilarious song is your new holiday anthem
The world's least visited destination is breathtaking!
LOL treadmill fail!
Google’s top searches of 2014

Jobs in Cape Town [change area]

Property [change area]

Travel - Look, Book, Go!

Kalahari.com - shop online today

2DAYS ONLY – 30% off Appliances

Coffee makers, blenders, fans, juicers and more. T&Cs apply. Shop now!

2 DAYS ONLY – 40% off books

Get 40% off when you buy 2 books. For two days only! T&Cs apply. Buy now!

Up to 50% off on outdoor gear

Save on chairs, blankets, cooler bags, umbrellas and more. Shop now!

Save on Samsung

Cameras, mobile phones, TVs, Tablets and more. While stocks last. Shop now!

Grand Theft Auto 5

Now available on PS4, Xbox One and PC from R649. Buy now!

OLX Free Classifieds [change area]

Samsung Galaxy s4

Mobile, Cell Phones in South Africa, Western Cape, Cape Town. Date October 24

Best bargain in big bay

Real Estate, Houses - Apartments for Sale in South Africa, Western Cape, Cape Town. Date October 25

VW Golf 6, 1.6 Trendline (Excellent condition)

Vehicles, Cars in South Africa, Western Cape, Cape Town. Date October 25

Horoscopes
Aquarius
Aquarius

You may be emotionally defensive or reserved today. You need to step up today as there may be extra responsibilities to deal with....read more

There are new stories on the homepage. Click here to see them.
 
English
Afrikaans
isiZulu

Hello 

Create Profile

Creating your profile will enable you to submit photos and stories to get published on News24.


Please provide a username for your profile page:

This username must be unique, cannot be edited and will be used in the URL to your profile page across the entire 24.com network.

Settings

Location Settings

News24 allows you to edit the display of certain components based on a location. If you wish to personalise the page based on your preferences, please select a location for each component and click "Submit" in order for the changes to take affect.








Facebook Sign-In

Hi News addict,

Join the News24 Community to be involved in breaking the news.

Log in with Facebook to comment and personalise news, weather and listings.