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Mapping planetary analogue terrains (for astronauts and the rest of us)

The tools needed to set up AGPA geophysical surveys during PANGAEA-X seem a bit threatening, but no one was harmed. Source: Flickr

Planetary science is practiced largely using remotely sensed data, remotely operated in-situ experiments, or extraterrestrial samples, either naturally delivered to Earth (meteorites) or collected and returned (sample return). An exception, so far unique, was the NASA Apollo program, where humans were mostly involved.

Both past and future planetary exploration of the Moon and Mars need to be planned and tested on terrestrial analogues, either for scientific or operational purposes. This can range from planning a rover traverse across terrains that resemble those to be encountered somewhere else in the Solar System, up to practicing for choosing the right sample to be targeted, analysed or collected.

Pangaea is the ESA program for astronauts providing training in geoscience as needed for their future planetary exploration tasks. Its roots are on the Apollo program, few decades earlier, although some of the tools used are the very same.

Analogue astronauts in Lanzarote, using Apollo-era tool replicas, with a somewhat more modern drone flying over — Source: Flickr/AGPA/@arosp

Surface and subsurface

In addition to basic geological training and related observations, geophysical and remote sensing experiments can be valuable for planetary exploration, either in the robotic or human-robotic case.

AGPA stands for Augmented field Geology and Geophysics for Planetary Analogues. The basic idea behind it is to use an integrated set of experiments to gather geological information on both the surface and subsurface. For now, just on a planetary analogue terrain. Future astronauts, either on the Moon or Mars, will most likely have to deploy and use geophysical equipment (as it was the case for Apollo missions, e.g. with seismics). They would also have the need to process and analyse data shortly after, in order to support, for example, reconnaissance robotic exploration of subsurface cavities and shelters.

Different types of experiment concur to AGPA: Remote Sensing via drones (AGPA-D), active laser scanning (AGPA-L) and different types of geophysical surveying, including passive and active seismics (AGPA-S) as well as geo-electrics (AGPA-G), i.e. probing the subsurface measuring its electrical properties via the so-called Electrical Resistivity Tomography (ERT).

A direct application of low-altitude, close-range remote sensing is stereogrammetry (AGPA-D), in which viewing the same surface with variable geometry allows its three-dimensional reconstruction.

Drone-based 3D reconstruction of the central part of Tinguatón volcano. For more, please check V. Unnithan and R. Pozzobon Sketchfab profiles

Compared to Apollo times, more tools are available, including laser scanning. Such active remote sensing can be very complementary to drone imaging as well as subsurface exploration and scanning (e.g. see this tweet from Tommaso Santagata/VIGEA).

In order to investigate the subsurface not directly accessible to humans or robots, other techniques and tools could be needed. That is where geophysics comes to help. In the case of the Lanzarote planetary analogue seismics (AGPA-S) and geo-electrics (AGPA-G) were used to try and image the subsurface expression of lava tubes. A similar approach could be used in the case of the Moon or Mars.

ESA Astronaut Matthias Maurer during field geophysics training: electrodes and hammer for electrode insertion (AGPA-G) in the soil are part of the kit. More tools and cables involved in the data acquisition are visible on Flickr.

Processing and analysis of collected data are still ongoing, including the integration of surface and subsurface remote sensing with geophysical probing. What one could already see in the early analysis during the field campaign is the expression of subsurface voids in the profiles.

AGPA geo-electric profile visualised short after its acquisition. Source: Twitter. Something not too dissimilar might one day be visualised during a Martian evening after a day of data acquisition in the field.

What about data?

We will use Zenodo and Pangea — yes another one, just without “a” — data repositories to store and share quotable data. Ultimately datasets will be also made available and discovered via the Planetary Virtual Observatory of EuroPlanet VESPA, which will link to either data source.

As an example, this is the first raw dataset released:

Unnithan, V., Rossi, A. P. Jaehrig, Tim. (2017) Drone-based photogrammetric survey raw data from ESA PANGAEA-X 2017 planetary analogue campaign — Data collected on 2017–11–19 [Data set]. Zenodo, DOI: 10.5281/zenodo.1084885.

Anyone could get and use the data. Once higher-level (i.e. processed) data are produced, they will be released in a similar manner, still on a data repository, but directly usable for visualisation and mapping.

AGPA image mosaic over Tinguatón, based on drone photogrammetric data. Source: AGPA for data, AgiSoft PhotoScan for processing, Google Earth Pro for visualisation. The white spot visible on the right of the image is this tent (more photos of the field location on the ESA astronaut training Flickr page).

While writing, data from both drone and ground-based laser scanning are being merged. What will come next is the integration with existing cave survey data, in order to have a complete surface-subsurface 3D model, at least for the Tinguatón volcano.

Animated GIF over the Tinguatón volcano: 3D point clouds from two sources, Drone photogrammetry (AGPA-L) and laser scanning (AGPA-D) Image source: D. Borrmann, H. Lauterbach, A. Nuechter, U. Würzburg.

If by any chance you plan to be at EGU 2018, AGPA as well as overall PANGAEA-X early results will be presented in session BG8.1/PS4.3.

With some more time (and weeks of processing time) AGPA is working on larger, better 3D reconstructions that will also be eventually released. In fact we do plan to release openly all data. And we started already with all raw data from the first day of data collection, November 19th 2017.

Some data handling tools, scripts and overall utilities are going to be posted on AGPA’s GitHub page, e.g. to support the geo-electric data analysis, or to help automate the upload of datasets to Zenodo.

The complete AGPA team at the entrance of one of the surveyed lava tubes.

Acknowledgements: We are grateful to AgiSoft for granting us the use of their software. ESA Pangaea-X specific acknowledgements are included in the above dataset.

For more information on AGPA, please feel free to get in touch.



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