Mars can seem amazingly Earth-like in many ways, and that includes weather. Bill Dunford recently posted some new images from the Mars Express spacecraft, providing some great views of Martian clouds as they drift over the landscape below. The one above is a beautiful example and all of them can be seen here. While Martian clouds don’t get as big and puffy as they can on Earth, they are still a reminder that Mars is a place, a world with its own unique history while at the same time reminding us of home.
With all of the attention that NASA’s rovers Opportunity and Curiosity have been getting, and deservedly so, we might forget sometimes that there are still other spacecraft orbiting Mars as well. NASA’s Mars Odyssey and Mars Reconnaissance Orbiter continue to return amazing high-resolution views of the planet from orbit, but there is also the ESA’s Mars Express, a European probe which is now celebrating its tenth year in orbit and still going strong.
The huge Grand Canyon is one of the greatest natural wonders on Earth, offering a glimpse into our planet’s dynamic geological history. But there is another canyon that is even larger, much larger – on Mars.
The idea that Mars used to be a “water world” and sort of like a smaller version of Earth in many ways is now pretty much accepted among planetary scientists; the debate continues however as to just how wet it was and for how long. The answer would have direct implications for the possibility of life ever having started there.
Two more pieces of the puzzle now suggest, or reinforce the notion, that Mars was indeed a much wetter place than the cold, dry desert we see today.
First, new findings regarding a discovery made by the Spirit rover a few years ago indicate that water was much more abundant and the atmosphere was probably at least twenty times thicker than it is now, which would have allowed surface water to exist.
The evidence comes from a rock fragment found embedded in volcanic sediment, known on Earth as a bomb sag since the sediment visibly “sags” below the rock as a result of the rock penetrating the sediment from the impact (after being ejected during a volcanic eruption).
Josef Dufek, an Assistant Professor at Georgia Tech University, has been studying the Martian bomb sag to see what it can tell us about conditions on Mars millions or billions of years ago. His findings were just published in the journal Geophysical Research Letters.
He re-created the bomb sag’s characteristics in the laboratory, to determine the conditions present when it originally formed. Using dry, damp and saturated sand beds to replicate the sediments, he found that only the saturated sand beds produced similar results to what is seen on Mars, indicating that the Martian soil was likely very wet when the bomb sag formed.
“Our study is consistent with growing research that early Mars was at least a transiently watery world with a much denser atmosphere than we see today,” said Dufek. “We were only able to study one bomb sag at one location on the Red Planet. We hope to do future tests on other samples based on observations by the next rover, Curiosity.”
Elsewhere on Mars, the Mars Express orbiter has taken new images of ancient water-carved channels in the Acidalia Planitia region, a huge basin in the northern lowlands. Like others on the planet, they show “dendritic” drainage patterns, typically formed by runoff of water from rain or melting snow.
While there is still no consensus on how long the watery period lasted on Mars, to what extent or whether it was a warm or colder environment, it seems certain that water did play a large role in shaping the terrain of the Red Planet early in its history. But then Mars somehow lost most of its water, while Earth continued to maintain its rivers, lakes and oceans. How that change occurred can teach us more about how Mars evolved as well as our own planet’s geological and biological history.
For a long time now, evidence has continued to indicate that Mars was once a water world – near-surface groundwater, lakes, rivers, hot springs and, according to some planetary models, even an ancient ocean in the northern hemisphere. That last one in particular has been a subject of intense debate; some scientists see evidence for it while others do not. Even if it was there, it may have been a warm ocean or it may have been colder, like the polar seas here on Earth. The prospect of an ocean of any kind on early Mars is an exciting one, regarding the question of possible life way back then. The argument has swung both ways over the years, but now another new report has been published which comes down on the “yes” side…
The Mars Express orbiter has taken new images of the large extinct volcano Tharsis Tholus on Mars. At about 8 km (5 miles) tall and with a base that stretches about 155 km x 125 km (96 miles x 78 miles), it is a medium-sized volcano for Mars, but is a giant compared to volcanoes on Earth. It has been noticeably battered over the eons.
The caldera on top is almost circular, thought to have formed when the magma chamber below finally emptied, causing the chamber roof to collapse under its own weight. Two other sections have also collapsed on the volcano’s western and eastern flanks, forming scarps up to several kilometres high.
Tharsis Tholus is just one of many volcanoes on the planet, although all of them are believed to have become extinct millions of years ago.
A few more updates in the last couple days or so regarding the evidence for past water on Mars. Previous evidence has continued to accumulate over the years, even for possible salty water still existing today in places. But three more recent findings add to this now as well.
First, in its brand-new exploration of Endeavour crater, the Opportunity rover has already found indications for past water activity, possibly hydrothermal. The first rock examined, Tisdale 2, showed very high concentrations of zinc and bromine, much more than previously seen before. On Earth, this usually means hot water moved around minerals, leaving deposits of zinc. This hydrothermal activity could be heated water or steam. But Opportunity still has a lot of work to do to sort out the details of this and other features of interest in this area, in particular the clays, which also point to water. The Spirit rover had already found strong evidence of hydorthermal activity at its landing site as well.
Second, the Mars Express orbiter has taken new photographs of an ancient delta in Eberswalde crater, which is thought to have been a lake a long time ago. Small feeder channels can also be seen, which would have filled the crater basin with water. This and other deltas, or what remains of them, are very similar to their counterparts on Earth.
Finally, a new report discusses evidence for a cold water ocean on ancient Mars. The long-running debate has usually been whether Mars was cold and dry or warm and wet in the past. This third option has gained more study recently, as it would help explain otherwise conflicting findings. There is a ton of evidence now that Mars was much wetter in the past, but still much debate over how warm it was, as some findings could be interpreted in different ways. The Martian ocean would have covered most of the northern lowlands, but new climatic and geophysical models suggest it would have been cold, not warm. Features around the edges, still visible, are consistent with glaciers. It would have been more like the polar seas, rather than the tropics, on Earth. So how does the evidence for lakes, rivers and hydrothermal regions fit into this? Still more questions than answers, it seems…