Fun Science: Iceberg Chasing and Laser Lights


Monaco glacier.
Credit: Storvik/AMASE

By: Juan Diego Rodriguez-Blanco (AMASE team)

One of the ‘fun science" activities we have carried out during AMASE 2009 is "iceberg chasing". Naturally this was all for a good scientific reason as we were interested in acquiring sediments trapped in calved icebergs for further characterization. Being in the arctic and around massive ice caps and glaciers it is no surprise that during the time we have been based on Lance we have seen tens of icebergs per day. Some of them are mostly made of blue ice but they sometimes also have layers of sediments and these are the interesting ones!

Why blue ice?

Blue ice occurs when the snow that fell on a glacier is compressed as a consequence of burying by more recent deposits of ice. This compression leads to the recrystallization of the ice crystals and thus they increase in sizes, permitting the light to travel slightly longer distances through it. As the light travels through the ice it is scattered, increasing the probabilities of absorption of both the red and yellow wavelengths, but not absorbing light at the blue end of the visible light spectrum. That is the reason the ice from glaciers is blue.

Therefore, when we see an iceberg that is made of blue ice, we know that it comes from an iceberg and it is not a recently frozen layer of sea ice. And that is our objective!

Why are we interested in blue-ice icebergs?

Iceberg made of blue ice floating in Wahlenbergfjorden. The darker areas are sediments trapped in ice.
Credit: Juan Diego Rodriguez-Blancoem>

In fact we are not interested in the ice itself: what we want to obtain is the sedimentary material that is trapped inside the ice that has calved from the massive glaciers. During the formation of a glacier, sediments are trapped in the ice and there they may remain over thousands of years. However, if the glaciers reach the ocean and calve icebergs these icebergs may contain trapped sediments. The amount of sediment in ice that is delivered to the oceans by glaciers can be as high as 1500 tons per year. However, the most interesting point is the fact that within these sediments there are mineral nutrients that are extremely important to support biological activity and that during entrapment the sediments may transform and react despite the cold temperatures. In terms of mineralogical changes we are looking for phases that affect the iron cycle.

So the task we have this year is: find a relatively newly calved iceberg, evaluate is it is safe to approach, find an interesting and safely reachable area with sediments, take samples, melt the ice and separate the sediments and than back in the lab study the sediments with different techniques (high resolution microscopy, X-ray diffraction, infrared spectroscopy, etc) with the specific question about the iron minerals.

We need to approach the iceberg carefully for inspection and to be completely sure that it is safe to take samples.
Credit: Juan Diego Rodriguez-Blanco

However, the reader will wonder why we do not just go onto a glacier and take the samples directly instead of chasing icebergs. In theory that may be better, but in the real world it is quite difficult, because we need blue glacier ice not located on or near the surface of the glacier or subglacial ice that could in some cases be collected from glaciers that end in a moraine and not calve into the ocean. In a previous blog entry I described the SLIce project which is also part AMASE 2009, and where we retrieved ice cores from the surface layers of glaciers and to a maximum depth of 1-2 metres; those cores are more than enough to study the extremophiles that thrive in surficial glacial ice as well as the -mostly few- sedimentary particles that these micro-organisms use to obtain nutrients. However, if we would aim to extract ice from bigger depths the task would be technologically much more complex. However, luckily glaciers that calve into the sea do most of the work for us and thus when sediments from deeper areas are needed, it is better to take them directly from icebergs, because the material that is interesting for us is exposed but still trapped inside the ice.

How do we chase icebergs?

Very very carefully!As usual on AMASE safety is the first rule. Although seemingly a simple task, approaching and sampling floating icebergs can be risky. Depending on the size and shape of an iceberg, even the smallest amount of pressure on it surface could lead to an iceberg to rotate or to flip upside down. Naturally, if this would happen when we approach an iceberg with a zodiac boat that would not be safe. Because 90% of the iceberg’s mass is under the water, its real size and shape is not easily evaluated, so we have to approach any iceberg carefully and evaluate whether we can safely obtain samples or not. If we see dirty blue ice, that means that there could be sediments waiting for us. So if the iceberg sampling is considered safe, the person that will take the samples will use an ice axe and a bag to catch the chipped of sections with sediments and ice. However, the ‘sampler’ will be secured by at least two people on the zodiac and the sampling will take less than five minutes/iceberg.

Sedimentary material trapped inside an iceberg. This is an extraordinary example, as most icebergs are not so ‘dirty’ as this one (left). Taking samples from the iceberg with an ice hammer. Our ship, the Lance, can be seen on the background (right).
Credit: Juan Diego Rodriguez-Blanco

This year three iceberg chasing trips have been carried out successfully, obtaining a total of samples from different icebergs. These samples will be returned to the University of Leeds where they will be studied further with the aim to provide novel information about the contribution of glacially derived iron-rich sediments to the iron-budget of the arctic ocean and their link to bioproductivity in the current ocean and also with respect to the Last Glacial Maximum (LGM). The samples collected this year will be compared and contrasted with other iceberg samples that have been collected during previous years in Antarctica and the Southern Ocean.

Studying the composition of Martian rocks: building and testing a new concept of Raman spectroscopy

Fernando Rull and Antonio Sansano studying rock samples on the ship with the contact Raman instrument.
Image Credit: Kjell Ove / AMASE

The next robotic Mars exploration missions that will fly to the Red Planet will focus the aim of their research on the "Search for life". Both the Mars Science Laboratory (NASA) and ExoMars (ESA) have this primary objective and thus they will need scientific tools to accomplish this task. The analyses of rocks and soils will be a priority and such analyses include elemental and mineralogical composition to possible organic molecules.

One of the worth mentioning analytical techniques that are being tested during AMASE 2009 is a Raman spectrometer. Two researchers are involved in a very interesting project that will be very important for both expanding the capabilities of the next missions to Mars and also for the detection of signatures of life on the Red Planet: Prof. Fernando Rull, who is the principal investigator of a contact Raman spectrometer for ExoMars, and Antonio Sansano, who is working with Prof. Rull on his PhD thesis. Both are working at the University of Valladolid, Spain, developing two Raman spectrometers that will obtain really valuable information about the chemical and mineralogical composition of the Martian rocks.

A detail of the contact Raman instrument.
Image Credit: Kjell Ove / AMASE

Raman spectroscopy is a process in which a monochromatic source (usually a laser) illuminates a sample, and this radiation is scattered by the matter of the sample. Most of the scattered radiation has the same wavelength -or frequency- as the incident radiation, but there is a very tiny (10-9) fraction that will be scattered with different wavelengths. This radiation, usually referred to as ‘secondary radiation’, was discovered by Sir Chandrasekhara Venkata Raman (1888-1970) winning the Nobel Prize in Physics in 1930.

Why is the ‘secondary radiation’ so interesting? Because it can give us plenty of data about the atomic-molecular vibrations of matter that we are illuminating with the laser light, enabling us to obtain structural and compositional information, as well as physical-chemical characteristics of solid, liquid or gaseous samples. Furthermore, one of the great advantages of Raman spectroscopy is that we only have to illuminate our sample with a laser, so -if the power of the laser is not too high- this is a non-destructive technique and the sample needs no prior preparation at all.

Considering the modern developments in spectrometry and optical fibre technology, as well as in miniaturization techniques for both spectrometers and detectors, it is not strange that Raman spectrometers could be really useful for planetary research missions. Although there were plans to include a Raman spectrometer aboard the Mars Exploration Rover missions, the devices were unfortunately discarded because of mass constraints for both probes. So the next mission that will include the first Raman spectrometer on Mars will be the EXOMars rover (ESA, 2019), that will acquire samples up to a maximum depth of 2 metres using a corer. These samples will be ground and transferred into small cache boxes located on a carrousel below various scientific instruments. Both the Raman spectrometer and an infrared microscopy will be the first instruments that will study the solid samples.

Fernando and Antonio preparing the remote Raman system in order to take measurements of blue glacier ice.
Image credit: Juan Diego Rodriguez-Blanco / AMASE

However, the Spanish team is not only developing this EXOMars contact Raman; they are working also on another project that is even more thrilling and that was also tested during AMASE 2009: a remote Raman spectrometer which coupled to an optical telescope makes it possible to measure samples located at a distance from 8 to 130 metres away, yet this spectrometer has the same precision as the contact Raman spectrometer. The potential of studying rocks and sediments from afar with an instrument like this would significantly expand the capabilities of a Martian rover or lander, because the combination of panoramic and high resolution cameras with Raman spectrometry would allow analytical information without moving the rover to the sampling areas to be obtained; this would save lots of energy and time. Although this technology is not yet miniaturized it has potential for future Mars sample return missions where this technology could be essential when time/distance, etc. constraints are very tight.

One of the field trips during AMASE 2009. While the group on the top is taking microbiological samples, Fernando and Antonio are obtaining measurements of glacier ice using the remote Raman system.
Image credit: Juan Diego Rodriguez-Blanco / AMASE

During AMASE 2009, both Rull and Sansano have analysed many different rock types that were part of several AMASE research tasks, they have participated in the AMASE 2009 SOWG (Science Operations Working Group) simulation of Mars rover missions and have shot a laser at a blue glacier ice from far away with the remote Raman, in order to evaluate the maximum distance from which ice -a very abundant compound in several planetary bodies- can be quantitatively analysed.