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True-colour image of Mars. The image was acquired in 2007 from a distance of about 240 000 km; its resolution is about 5 km/pixel.

By Miguel A. de Pablo and Juan D. Centeno Do you know the composi- that Mars had liquid water millions tion of the Martian polar of years ago – flowing on its surface, caps? filling the basins of impact craters, t the expected time, the orbiter, forming lakes, flowing downslope of The northern polar cap of flying at about 300 km in alti- some volcanoes’ flanks, from the Mar- Mars is mainly H O ice. tudeA and around 3.5 km.s-1, focused 2 tian highlands to the lowlands, where However, the southern toward the surface of the arid, cold an extensive ocean could have existed polar cap comprises H O and reddish planet and opened the 2 (referred to as Oceanus Borealis). ice and CO2 ice. shutter of the complex and precise BACKGROUND Solid water is a different matter. Ice camera. A new image from the Mar- polar caps on Mars were identified tian surface, and gigabytes of data, from telescopes and clearly recognis- were then recorded at the same time. – never before have so many experts able on orbiters’ imagesw6, and frozen This process has been repeated many shared so much information and pro- soils have been confirmed in several times in recent decades by the differ- duced so many models and results. places on the planet, mostly thanks to ent orbiters, landers and roversw1 that we have sent to our nearest planet. Water and ice on Mars Every new image and data set increas- One of the scientists’ main interests w2,w3 es the incredibly huge database in Mars research is water. Is there Image courtesy of ESA of information on Mars. Scientists water on Mars? Where is it? Is it liquid from all around the world use these or frozen? In the past, were there resources to study the planet’s chemi- oceans, seas, lakes and rivers on Mars? cal, physical, climatic and geological How did they disappear? Is their environment, with the aim of under- disappearance related to the past and standing more about Mars and how present climate of the planet? But also: it – and even Earth – has evolved. This Is there, or was there, life on Mars? widespread availability of imagesw4 And could humans live there one day? and data is one of the most amazing Thanks to the data acquired by orbit- phenomena in the history of science ers, landers and roversw5, we know The ExoMars rover

12 I Science in School I Issue 28 : Spring 2014 www.scienceinschool.org Cutting edge science

Image courtesy of NASA/JPL/HiRISE/University of Arizona

HiRISE image of Mars from NASA’s Mars Reconnaissance Orbiter mission, showing the surface with very high resolution (0.35 m/pixel), enough to identify features as small as 1 m in size.

ence of ice and glacial-related features using new high-resolution (as high as 35 cm/pixel) images acquired by the active missions of NASA and the European Space Agency (ESA). Our research group focused on the north- west flank of the Hecates Tholus vol- Physics cano in the Elysium region of Mars,

Ages 10-11+ at tropical latitudes of the northern Earth science The article is interesting hemisphere. We analysed all the avail- because the teachers and able images from different orbiters stu­dents can understand covering this region (at different spec- that currently research can mean temperature of Mars is about tral, temporal and spatial resolutions), be done if you spend many -80 ºC during daytime; at the Equa- and observed features that we inter- hours in search of free inter- tor, the sunny slopes in the summer at preted to be caused by glacial erosion national databases, if you or sedimentation: moraines, crevasses, noon hours can reach a surface temp­ Physics compare many images and erature of 15 ºC. roches moutonnées, glacial cirques, of course if you have ex- hanging valleys, eskers, drumlins or arêtes, among othersw9. pertise in a scientific field. Studying martian glaciers Then you can emit a theory Our interpretations were based on w7 which has to be proved by Today, research on Martian ice fo- the comparison between the mars- another research and so on. cuses on finding evidence of the pres- forms (the reliefs observed on Mars) The supplementary links Image courtesy of NAS/JPL/HiRISE/University of Arizona and educational resources can be the starting point for inquiry based learning projects with the title like these: Earth and Mars Simi- larities, Studying the Mars Planet or Life on Mars. Corina Lavinia Toma, Com- puter Science High School “Tiberiu Popoviciu”

REVIEW Cluj Napoca, Romania

the images reported by NASA’s Phoe- nix mission at high latitudes. The low temperatures of the planet through- out the year, measured by different This unusual structure with traces of a glacier is located in Promethei Terra at the landers and rovers (such as Viking I eastern rim of the Hellas Basin. A so-called ‘block’ glacier flowed from a flank and II, Mars Pathfinder, Spirit, Oppor- of the massif, past mountains several thousand metres high, into a bowl-shaped tunity and Curiosity, which arrived on impact crater, nine kilometres wide, which has been filled nearly to the rim. The Mars in August 2012), confirm that block glacier then flowed into a 17 kilometre wide crater, 500 metres below, ice is stable at all latitudes. In fact, the ­taking advantage of downward slope. www.scienceinschool.org Science in School I Issue 28 : Spring 2014 I 13 Did you know that Mars had

Images courtesy of NASA/JPL/University of Arizona ice ages? Polygonal terrain near the northern po- Crater counting has provided lar cap of Mars, where water ice was evidence of glacial activity, observed just a few centimeters below both ancient (more than 1000 the surface. million years ago) and recent (less than 2 million years ago). The cold periods in Mars history are related to orbital changes (mainly changes to spin axis angle) – just like Earth, where the orbital cycles control most of the Quaternary climate change, as discovered by Milutin

BACKGROUND Milankovic in 1922!

Images courtesy of NASA

Polygonal terrain, typical of frozen soil areas on Earth, surrounding the Phoenix landing site.

and the terrestrial landforms in the work in front of the computerw8 and Alps, Iceland or Antarctica, where on different field trips, and thanks to we conducted fieldwork looking for the satellite images and topographic, terrestrial analogues. We also used spectrometric and thermal data, we the ‘multiple working hypotheses’ carried out a detailed description, scientific method to discard other pro- mapping and age determination of the cesses that are able to produce similar features observed on the flank of the features as the origin of the marsforms Martian volcano. Our first conclusion, we observe. Then, after months of based on the long list of glacial-related features on the Hecates Tholus vol- cano, is that an important amount of ice existed there for a long time, form- ing glaciers that flowed downslope, Did you know that Martian sculpting the flanks of the edifice. ­volcanoes had glaciers? The problem is… we couldn’t find Many Martian volcanoes ice anywhere! However, we could see show reliefs on their flanks some glacial features that we know that are caused by glacial can’t survive for long after ice melts. ice flows – just as we see on This is the case for crevasses: fractures Earth. Those volcanoes are in the glacier disappear when ice located not at polar but at melts or sublimates. We didn’t see the tropical latitudes. Olympus ice on this part of Mars, but we could Mons, Ascraeus Mons and recognise the crevasses sculpted in the View of the Hecates Tholus volcano, Hecates Tholus are examples dust layer that covers the ice. For that in the Elyisum region of Mars, and of volcanoes with glaciers, reason, our second conclusion is that the area in which glacial marsforms similar to Mount Kiliman- the ice causing the extensive fields of have been observed. The area was jaro (Tanzania) and Cotopaxi glacial marsforms must still be below chosen because its high concentration of glacial forms found during general ­(Ecuador) on Earth. the surface – or it melted very, very BACKGROUND exploration of the volcano slopes. recently.

14 I Science in School I Issue 28 : Spring 2014 www.scienceinschool.org Cutting edge science

Partial view of the geomorphological map showing multiple glacial-related

features, highlighting the potential Earth science glacier tongues. Colours are part of a conventional map legend: blue hues Image courtesy of Miguel A. de Pablo and Juan D. Centeno represens glacial areas.

A B Images courtesy of HiRISE/UA/NASA and DigitalGlobe

Similarities between marsforms in Physics Hecates Tholus (A) and landforms in Deception Island, Antarctica (B) help scientists to deduce their origin – in this case, glacial ridges are observed in the images (black arrows).

A B

Crevasses (fractures on the ice due to its flow) on Hecates Tholus (A) and on glaciers on Deception Island, Antarctica (B), where they are cov- ered by volcanic deposits from the last eruption in 1970.

Future steps Image courtesy of HiRISE/UA/NASA and DigitalGlobe We plan to repeat our observational study in other volcanic regions on Through crater counting (see box its ­northwestern flank. In fact, we Mars to see if the same pattern exists p.17), we also calculated the age proposed the existence of cold and to get a better idea of the global of the different glacial deposits that ­periods, in which the ice tongues distribution of glaciers and ice on we observed on the images. We covered an important part of the vol- Mars. These studies will further our found a wide range of ages – from cano and its surroundings, and also understanding of the climate, its evo- 1000 million years to 350 000 years – warmer periods, in which the glaciers lution and its characteristics on our which means that the Hecates Tholus were smaller and covered only parts neighbouring planet. The presence of ­volcano had a long history in of the flank, such as in the present glacial features on volcanic edifices which the glaciers slowly sculpted time. could also mark the location of sites www.scienceinschool.org Science in School I Issue 28 : Spring 2014 I 15 Image courtesy of NASA/ESA/JPL-Caltech/University of Rome/Washington University in St. Louis

Mars northern polar ice cap section, based on ground penetration radar rative and interplanetary effort to data showing the ice and sediments Did you know that liquid ­further science. layers. water is not stable on Mars? Web references All the water that has been found on Mars exists in a w1 – NASA’s Mars Exploration Mis- Mars. See: http://ode.rsl.wustl. gas or solid state. Mars’ sions website provides informa- edu/mars/ atmospheric pressure is very tion on all the past, present and w6 – The Mars Odyssey’s THEMIS low (around 6 mbar, com- future missions to Mars by differ- has generated many images that pared with Earth’s average of ent countries and space agencies. can be searched by topic (including 1013 mbar) and below the See: http://mars.jpl.nasa.gov/­ ice-related topics). The site is useful minimum required for liquid programmissions/missions/ for learning and develop of didactic BACKGROUND water stability. w2 – The Planetary Science Archive of activities. See: http://themis.asu. the ESA stores data from planetary edu/topic and universe exploration missions. w7 – The website of the Mars Ice where life, if it existed, could have It is free to use. See: www.rssd.esa. Consortium contains links to free found water and heat to survive, even int/PSA educational resources about Mars in the cold and dry environment on w3 – NASA’s Planetary Data System from different institutions. See: Mars. stores all the data from the plan- www.mars-ice.org Upcoming studies will use a new etary and universe exploration mis- kind of tool: penetration radar. This w8 – JMars is a freeware and multi- sions. It is free to use. See: http:// platform Geographic Information technique allows us to measure the pds.nasa.gov/ properties of materials below the System that is used by planetary w4 – The All Mars images webpage surface and to investigate their varia- scientists to visualise different types from Arizona State University of data from Mars, such as images, tions: if there is ice below the surface, (USA) shows all the images from topography, spectrometry and many it should be distinguishable in the Mars acquired since the Viking mis- other data. The site requires free radar data, just as we observed in sions in the late 1970s. To investi- registration and can be found at the Martian polar caps. Radar data gate this user-friendly resource, see: http://jmars.asu.edu/ from NASA and ESA will allow us http://themis.asu.edu/maps to corroborate our interpretations of w9 – You can search for glacier-related observations from the Hecates Tholus w5 – The Mars Orbital Data Explorer terminology and photos on the glaciers and other areas on the red has a user-friendly search tool to Glaciers online photo glossary planet, thanks to a modern, collabo- extract data from any mission to for secondary education. See:

16 I Science in School I Issue 28 : Spring 2014 www.scienceinschool.org Cutting edge science

Do you know how scientists estimate the age of the sur- faces of Mars?

Image courtesy of NASA/JPL/Corby Waste Image courtesy of NASA/JPL/Corby It is simple and efficient: they count the craters left by me- teorites after their impacts on the surface of Mars – and any

other planet or moon. High Earth science crater density corresponds to Artistic illustration showing NASA’s old surfaces and low crater Mars Reconnaissance Orbiter passes density is linked to young above a portion of the planet called

BACKGROUND surfaces. Nilosyrtis Mensae Physics www.swisseduc.ch/glaciers/­ Ever thought of visiting Mars? This of Alcalá in Madrid, Spain. He is a glossary/index-en.html book might give you all the good- geologist and has focused his interests tips to do so: on Mars since 1996. He has experience References Hartmann WK (2003) A travel- in geological and geomorphological De Pablo MA, Centeno JD (2012) ers’ guide to Mars. USA:Workman cartography, volcanism and glaciers, Geomorphological map of the lower Publishing Company. ISBN: 978- which he has studied in Iceland and NW flank of the Hecates Tholus vol- 0761126065 Antarctica. He is also a member of the Science Team of NASA’s Mars Science cano, Mars (scale 1:100,000). Journal To learn more about the story of water of Maps 8: 208-214 Laboratory on Curiosity. on Mars, see: Juan D. Centeno is Associate Profes- Resources Carr MH (1996) The water on Mars. sor at the University Complutense in Oxford, UK: Oxford University Madrid, Spain. He is also a geologist The Google Earth freeware allows Press. ISBN: 978-0195099386 with more than 25 years experience viewers to visualise images at differ- teaching geomorphology and environ- ent resolutions and scales not only To lean more about the geology of mental geology and studying glacial, of Earth but also of Mars (and the Mars, see: periglacial and granitic landscapes all Moon). and can be used to make Carr MH (2006) The surface of Mars. around the world. comparative analysis. See: www. Cambridge, UK: Cambridge Univer- Miguel and Juan are now working google.com/earth/index.html sity Press. ISBN: 978-0521872010 together to study glacial landforms in The Google Mars webpage contains To learn more about the evolution of the flanks of the Hecates Tholus vol- a simple map of Mars with topog- the climate on Mars, and how it was cano of Mars. raphy, and mosaics of visible and once wet and warm, read: infrared images. See: www.google. Kargel JS (2004) Mars: a warmer com/mars/ and wetter planet. Chichester, UK: To learn more about the history and Springer-Verlag/Praxis. ISBN: 978- evolution of Mars, see: 1852335687 Forget C, Costard F, Lognonné P

(2006) Planet Mars: story of another To learn how to world. Chichester, UK: Springer-Ver- Miguel Ángel de Pablo is an use this code, see lag/Praxis. ISBN: 978-0387489254 ­Assistant Professor at the University page 57.

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