Determinación de albedos, firmas espectrales y su

Albedos and spectral signatures determination and it connection to
geological processes: Simile between Earth and other solar system
bodies
Javier Eduardo Suarez Valencia, Fabián Saavedra Daza, Luis Hernán Ochoa
[email protected], [email protected], [email protected]
Introduction
Pluto
In this work were used surfaces albedos, electromagnetic spectral data and
satellite imagery looking to understand the glaciers dynamics in some solar system
bodies; and how this is related whit their compositions and associated geological
processes. By specialized software we were able to create reflectance maps and
make geomorphological analysis that allows the differentiation between ice types in
the glaciers and to see its interactions whit other materials. The satellite images
were examined in the visible to mid-wave infrared region of the spectrum; then the
spectral signatures were use to connect the reflectance whit the chemical and
rheological properties of the studied compounds.
The albedo or reflectance is the amount of radiation that a surface is capable of
reflect in regard to the incoming radiation; if the reflected energy is big also will be
the albedo (usually between 0 and 1). The DN (Digital Number) is the magnitude
assigned to a pixel in the satellite images, applying a conversion factor is possible
to obtain the real reflectance.
Figure 3: Reflectance maps in the Sputnik Plateau region in Pluto, blue color correspond to ware ice,
brown to organic mater influenced ice, and yellow to CH4 ,CO and N2 ices.
Mars
Method
The Earth images are products of Landsat 8, the ones of Pluto were captured by
the spacecraft New Horizons; both were worked using the software ArcGIS 10.1.
For Mars were selected captures taken by the HiRISE cam in the MRO spacecraft
(Mars Reconnaissance Orbiter) and were studied whit the software Hiview. The
Nevado del Ruiz spectral signature was obtained by EO-1 satellite data processed
in the software ENVI.
Results
Figure 4: DN distribution for the pixels in the pointed areas, every type of surface has a unique
dispersion.
Earth
Spectral Signatures
Figure 6: Spectral signature (reflectance) for Pluto
surface, it can be distinguee CH4 ,CO and N2
signatures (taken from Cruikshank, 2014) .
Figure 1: “Parque natural nacional de los nevados”: Visible range in the left, and the 7-4-1 band
composite to the right (ideal combination for water ice detection).
Figure 7: Spectral signature (reflectance) of a
Martian glacier in black, CO2 spectral signature in
red and H2O signature in blue (Taken from
Birbring, 2004).
Figure 5: Spectral signature (reflectance) for
Nevado del Ruiz glacier, it can be observed
similar pattern to the water ice.
Conclusions
•
•
Figure 2: Reflectance maps in the Nevado del Ruiz glacier, A) Reflectance in the NIR ( NearInfrared), B) Reflectance in the visible.
References
•
Fengming HUI et al., (2014), Mapping blue-ice areas in Antartica using ETM+ and MODIS data.
•
Stern et al. (2015), The Pluto system: Initial results from its exploration by New Horizons.
•
Whinter (1993), Landsat TM derevied and ni situ summer reflectance of glacier in Svalbard.
•
Song et al (2001), Classification and Change Detection Using Landsat TM Data: When and How to Correct Atmospheric
Effects?.
•
Cruikshank (2014), The surface composition of Pluto and Charon.
•
Bibring (2004), Perennial water ince identified in the south polar caps of Mars.
•
The reflectance for water ice bodies are very high in the visible range and low in the
NIR, this relation becomes inverse in silicate materials as volcanic ashes. The last
allow reflectance maps to be optimums in the identification of other materials present
in glaciers of water ice; and to understand the temporal evolution of recurrent volcanic
activity zones, like Nevado del Ruiz.
The albedo analysis
is a efficient method to differentiate
materials of a
heterogeneous surface; the distinct reflectance's of the ices in Pluto surface allowed
a good discrimination based in the radiation that reflects every material. However, its
necessary the apply of spectral signatures to obtain approximated chemical
compositions of the icy bodies. The combination of this two methodologies is
essential to understand the glacier dynamics in other solar system bodies.
The level of correlation between the processes happening to glaciers in Earth and
those in other solar system bodies rely on the surface conditions of every body; the
low temperatures of Pluto drive the water ice to behave as solid rock, while other
materials like CH4 ,CO and N2 behave very plastic and low resilient. In Mars the
conditions aren't to different to Earth, the glaciers go trough similar processes in both
planets, yet in the Martian poles CO2 ices and snow can be accumulated, allowing
unique processes such as linear gullies.