This week’s geoscience roundup, for 7-13 February, is one of the more eclectic ones. All sorts of interesting new pieces of research have popped up on my Twitter and other social media feeds, and I’ve picked a mixture that might intrigue or concern you — or in a couple of cases, both.
If there is a theme this week, it’s a fairly tenuous one — the enduring links between what’s happened in the past, what’s happening now and what might happen in the future. These operate on scales from the planetary to the here and now.
Is There Liquid Water on Mars?
For the first piece of research this week, I’ll pick up on one of the pieces I discussed last week: the existence of water in extra-terrestrial bodies. Is there liquid water on Mars may not be quite as catchy a phrase as is there life on Mars, but the two phrases might be interchangeable. For the existence of life we need liquid water.
It’s been established that there is ice on Mars, as in other places in the solar system, but what we don’t know is whether there is any accumulation of liquid water. This week a new study was published that considered the possibility.
Beginning from the starting point that: “Recent radar observations from the European Space Agency’s Mars Express spacecraft have been interpreted as evidence for melting beneath the ice at the south pole of Mars” the research, from the University of Arizona, considers what we know of environmental conditions on Mars to see what circumstances would need to exist for liquid water to be present.
The study doesn’t reach a conclusion one way or the other, but it’s an interesting read nevertheless. Assuming the most favourable conditions (heavy concentrations of salts which raise the freezing temperature of ice) at the base of the ice caps, the modelling implies that even in this situation, the colder temperatures on Mars (the study used an average surface temperature of 162K) don’t allow liquid water to exist.
This isn’t the end of the story, however. There are other reasons why liquid water might exist other than a high concentration of salts one of which is some source of internal heat. There’s certainly evidence of this on Mars, in the form of volcanic landforms, though none of these are currently active, but it may be that there is subsurface volcanism which has not yet detected.
Bearing this in mind the study, while ruling out the existence of liquid water without some form of planetary heat, concluded that there might be, with the addition of a magma chamber beneath the polar ice cap: “Under this scenario, the magma chamber must have been emplaced in the upper 10 km of the crust … 100s of kyrs ago, due to the time lag for heat to conduct… If the magma can attain depths of 5 km or less, it may be able to cause basal melting without any significant salt content in the ice”.
Ice Retreat Reveals Ancient Plant Forms
The second article this week is another take on ice and life, this time on our own planet, and is based on an assessment of plant material preserved beneath newly-lost ice cover in the Canadian Arctic. The study is fascinating at two levels, the first being the revelation of what plant life was like in the region millennia ago and the second being that it gives us an indication of the extent of Arctic ice loss in terms of cyclical ice cover.
Researchers collected plant material from the ice margins at 30 sites in Canada, where ice has recently retreated. (As melting can be affected by local conditions, the number of sites helped to reduce the chances of an anomalous conclusion.) Dating the plant material (using radiocarbon dating) gives an indication of the time those plants were killed by advancing ice and thus of the last date at which a particular site was ice-free.
The results of the study showed that: “Enhanced ice retreat due to warming summers has exposed entombed plants, still in growth position, that yield >40 ka plant 14C ages from the margins of 30 unique ice caps”. In other words, the ice cover in those sites had been in place for 40,000 years and has only recently been uncovered.
Further modelling in the study leads to an alarming conclusion: “Viewed in the context of temperature records from Greenland ice cores, our results suggest that summer warmth of the past century exceeds now any century in ~115,000 years”.
Evidence of Past Volcanic Tsunami in the Mediterranean
One of the major geoscience stories of 2018 was the eruption of Anak Krakatau volcano in Indonesia, and the subsequent tsunami that killed hundreds. Normally we associate tsunamis with earthquakes but the December 23 event was a classic illustration of an alternative cause — a volcanic eruption causing the collapse of a large mass of material either under or into the sea.
The Krakatau eruption had been described as a possibility beforehand, and such events are not unknown at active, steep sided volcanoes whose slopes are unstable. In the past it hasn’t always been possible to link an eruption (or an earthquake) with a tsunami because of the distance between them.
Reconciling different strands of evidence can, however, establish a link and new research into Stromboli, a European volcano, has established the existence of past collapses of the volcanic slopes and linked them to geological evidence of tsunamis both on the island itself, leading to its abandonment by locals, and elsewhere. The research concludes that: “three unprecedented well-preserved tsunami deposits related to repeated flank collapses … occurred during the Late Middle Ages”.
The study is fascinating in itself as a reconstruction of past events and an example of how we can pick out key events in history where the written record is limited, but it’s also highly significant in that it demonstrates that the risk of a collapse, such as that seen at Krakatau, occurring at Stromboli is higher than previously thought.