Geoscience Reference
In-Depth Information
Table2. Characteristicemissionlineofanaurora
spectrum.
Wavelength
(nm)
Molecule/atom
Height (km)
N
+
391.4
1,000
N
+
427.8
1,000
557.7
O
90-150
630.0
O
>
150
636.4
O
>
150
661.1
N
2
65-90
669.6
N
2
65-90
676.8
N
2
65-90
686.1
N
2
65-90
3.1.
Meteors on Mars
As we have seen, on Earth a meteor occurs when a meteoroid interacts
with the atmosphere between 120 and 70 km. A part Mercury and Pluto, in
principle, all the solar system planets (even the Saturn satellite, Titan, and
Neptune satellite, Triton) have su
ciently dense atmospheres to generate
meteors. Mars is a planet where meteors could be easily observed.
In spite of the difference in the chemical composition of the Earth and
Mars atmospheres, at the same conditions (atmosphere density, meteoroid
mass, and velocity), the meteors show the same luminosity because less
than 3% of the trail emitted radiation is produced by atmospheric atoms.
Considering the same meteoroid mass and velocity, the meteors on Mars
occur about 20 km lower.
1
Meteors on Mars are very similar to the terrestrial ones, thus the instru-
ments designed for observation from orbit of terrestrial meteors can also be
used for the observation of Martian meteors.
3.2.
Meteors on Venus
Meteors on Venus could be observable from orbit and, due to the higher
density of the Venusian atmosphere, the interval 120-70 km for the meteors
on Earth corresponds to 300-200 km on Venus. This means that the appar-
ent brightness from orbit will be higher with respect to a similar event on
Earth. Moreover, the height where the meteor phenomenon occurs on Venus
is larger than the haze and cloud upper limit (80 km), allowing the obser-
vation from space. Assuming a height of 600 km and a distance of 250 km
from the Venusian meteor, we estimate that on Venus meteors are appar-
ently 0.2 magnitudes brighter than on Earth. So, as in the case of Mars,
