Mars Express discovers aurorae on Mars (Forwarded)

ESA News
http://www.esa.int

9 June 2005

Mars Express discovers aurorae on Mars

ESA's Mars Express spacecraft has for the first time ever detected an aurora
on Mars. This aurora is of a type never previously observed in the Solar
System.

Observations by the SPICAM instrument (SPectroscopy for the Investigations
and the Characteristics of the Atmosphere on Mars) taken on 11 August 2004,
revealed light emissions now interpreted as an aurora.

Aurorae are spectacular displays often seen at the highest latitudes on Earth.
On our planet, as well as on the giant planets Jupiter, Saturn, Uranus and]
Neptune, they lie at the foot of the planetary magnetic field lines near the Poles,
and are produced by charged particles -- electrons, protons or ions - precipitating
along these lines.

Aurorae have also been observed on the night side of Venus, a planet with no
intrinsic (planetary) magnetic field. Unlike Earth and the giant planets, venusian
aurorae appear as bright and diffuse patches of varying shape and intensity,
sometimes distributed across the full planetary disc. Venusian aurorae are
produced by the impact of electrons originating from the solar wind and precipitating
in the night-side atmosphere.

Like Venus, Mars is a planet with no intrinsic magnetic field. A few years ago it
was suggested that auroral phenomena could exist on Mars too. This hypothesis
was reinforced by the recent Mars Global Surveyor discovery of crustal magnetic
anomalies, most likely the remnants of an old planetary magnetic field.

SPICAM detected light emissions in the Southern hemisphere on Mars, during
night time observations. The total size of the emission region is about 30 kilometres
across, possibly about 8 kilometres high. Whilst the detected emission is typical for
day-time, it must indicate the excitation of the upper atmosphere by fluxes of
charged particles -- probably electrons -- if observed during night-time.

By analysing the map of crustal magnetic anomalies compiled with Mars Global
Surveyor's data, scientists observed that the region of the emissions corresponds
to the area where the strongest magnetic field is localised. This correlation
indicates that the origin of the light emission actually is a flux of electrons moving
along the crust magnetic lines and exciting the upper atmosphere of Mars.

SPICAM observations provide for the first time a key insight into the role of the
martian crustal magnetic field in producing original cusp-like magnetic structures.
Such structures concentrate fluxes of electrons into small regions of the martian
atmosphere. Eventually, they induce the formation of highly concentrated aurorae
whose formation mechanism -- a localised emission controlled by anomalies in the
crust's magnetic field -- is unique in the Solar System.

Note to editors

The martian aurora was observed in the Mars region corresponding to 177 degrees
east and 52 degrees south.

These results appear in the 9 June issue of the scientific journal Nature.

The authors of the findings a J-L. Bertaux, SPICAM Principal Investigator,
F. Leblanc, E. Quemerais (Service d'Aeronomie du CNRS/IPL, France),
O. Witasse (European Space Agency - Noordwijk, The Netherlands), J. Lilensten
(Laboratoire de Planetologie de Grenoble, France), S.A. Stern (Southwest
Research Institute, Colorado, USA), B. Sandel (Lunar and Planetary Laboratory,
University of Arizona, USA), O. Korablev (Space Research Institute-IKI, Moscow,
Russia).

For more information please contact:

Agustin Chicarro
ESA - Mars Express Project Scientist
E-Mail: agustin.chicarro @ esa.int

Olivier Witasse
ESA -Huygens Operations Scientist
E-mail: olivier.witasse @ esa.int

Related links

* Looking at Mars
http://www.esa.int/SPECIALS/Mars_Express/index.html
* Orbiter instruments
http://www.esa.int/SPECIALS/Mars_Exp...C75V9ED_0.html
* Nature
http://www.nature.com

IMAGE CAPTIONS:

[Image 1:
http://www.esa.int/esaCP/SEMLQ71DU8E_index_1.html]
First aurora ever detected on Mars

Terra Cimmeria is the area in the southern hemisphere of Mars where Mars
Express has detected for the first time ever an aurora in the Red Planet. The
aurora was detected at 177 degrees east and 52 degrees south. It is linked
to anomalies in the crustal magnetic field, and it has a highly concentrated
shape, making it unique in the Solar System.

Credits: NASA/ESA

[Image 2:
http://www.esa.int/esaCP/SEMLQ71DU8E...html#subhead1]
Mars aurora is related to crustal magnetic field

A martian aurora has been detected by the SPICAM instrument on board
Mars Express on 14 August 2004. Its emission, 30 km across and about 8 km
high, corresponds to an area where the crustal magnetic field is very strong
(dark red in the image).

Credits: NASA, MGS