THE ATMOSPHERE OF TITAN

Jorge Hernández ArceFísica del Sistema SolarMaster en Astrofísica UCM-UAM

Content

A little history Characteristics of the moon’s atmosphere

General properties. Composition.

Similarities with Earth’s atmosphere and their meaning.

Cassini and Huygens References

A little history

First suspicions of an atmosphere Comas i Solá (1903).

Confirmed by Kuiper in 1944. First detailed images of the moon obtained by

Voyager 1 in 1981 discovering that the atmosphere was, in fact, denser than the Earth’s.

Already in the 21st Century the probe Huygens, part of the spacecraft Cassini, succesfuly landed in the moon’s surface.

Characteristics of the moon’s atmosphere

As aforementioned, it’s actually denser than the Earth. The surface pressure is about 1.47 times greater.

Given this density, and the low gravitational force of the satellite (1.35 m/s2), the atmosphere is much more extent than ours, its effects being appreciable even at 1000 km of altitude.

Characteristics of the moon’s atmosphere

The main gases that compose Titan’s atmosphere are: Nitrogen (98.4 %) Methane (1.4%) Hydrogen (0.1-0.2%) Trace amounts of ethane, diacetylene,

methylacetylene and other hydrocarbons. Also traces of other gases such as cyanoacetylene,

hydrogen cyanide, carbon dioxide, etc.

Characteristics of the moon’s atmosphere

Here is the atmospheric composition at different altitudes:

Similarities to Earth’s atmosphere

The main similarity is the atmosphere’s density and composition. It’s roughly as dense as Earth (just a little denser) and shares the same major component (nitrogen).

There is evidence of rain on the surface of the planet, although it doesn’t rain water, but methane.

There is a high amount of organic compounds in the atmosphere, as aforementioned.

In high latitudes there are lakes of liquid methane, whereas near the equator Titan is more arid, although there are signs of the presence of liquids.

Similarities to Earth’s atmosphere

All these similarities, specially the organic compounds, lead to believe that Titan is the most probable candidate to accomodate life outside of Earth, although it is still highly improbable due to other conditions ( the surface temperature is 92 K in average).

The presence of liquid methane ensures the lack of oxygen given the fact that it would cause the methane to burn.

Cassini-Huygens

It is a joint project of NASA, ESA and ASI (Italian Space Agency).

Launched on 15th of October 1997 and arrived to Saturn the 1st of July, 2004.

The part specifically designed to study Titan is the Huygens probe, which separated from the main spacecraft the 25th of December 2004 and landed in the satellite’s surface on the 14th of January of the next year, 2005.

Cassini-Huygens

The Huygens probe is equiped with the following instruments: Aerosol collector an Pyrolyser

(ACP) Descent Imager/Spectral

Radiometer (DISR) Doppler Wind Experiment

(DWE) Gas Chromatograph and Mass

Spectrometer (GCMS) Huygens Atmosphere Structure

Instrument (HASI) Surface Science Package (SSP)

Cassini-Huygens

The probe’s most important findins are: The aforementioned methane cycle.

There are lakes of liquid methane, fed by rain of this same molecule together with organic ones.

Winds in the direction of rotation of the moon, between 60 and 100 km/h.

Solid surface of Titan is orange, and spongy, can be compared with yogurt.

Possibility of a past volcanic activity with ice an ammonia instead of lava.

The surface temperature is around 90K.

References

Biemann, H. B., Atreya, S. K. et al. 2010 Journal of Geophysical Research. V. 115.

Turtle, E. P., Perry, J. E., et al. Science V. 331 2011

Yung, Y. L., Allen, M. et al. The Astrophysical Journal Supplement Series, 55:465-506, 1984.

Rodriguez, S.; Le Mouélic, S. et al. Nature 459 2009.

http://www.esa.int/esaMI/Cassini-Huygens/index.html