Analysis of the satellite data indicates that Mars appears to lack
active plate tectonics(carencia de actividad tectónica de placas)
at present(en la actualidad); there is no evidence of
recent lateral motion of the surface(corrimiento de tierras).
With no plate motion, hot spots(puntos calientes, activos)
under the crust(corteza) stay in a fixed position relative
to the surface; this, along with(junto con) the lower
surface gravity, may be the explanation for the giant volcanoes. However,
there is no evidence of current volcanic activity. There is evidence of
erosion caused by floods(inundaciones) and small river
systems. The possible identification of rounded pebbles(guijarro)
and cobbles(adoquines) on the ground, and sockets(cuencas)
and pebbles in some rocks, suggests conglomerates that formed in running
water(agua corriente) during a warmer past some
2-4 billion years ago, when liquid water was stable and there was water on
the surface, possibly even large lakes(glagos) or
oceans. There is also evidence of flooding that occurred less that several
million years ago, most likely(más que probablemente)
as the result of the release(liberación) of water from
aquifers(acuíferos) deep underground(en las
profundidades del subsuelo).
Seasonal Changes(cambios estacionales)
Because the axis of rotation is tilted(inclinado) about
25° to the plane of revolution, Mars experiences seasons somewhat(algo)
similar to those of the earth. One of the most apparent seasonal changes is
the growing or shrinking(encogimiento, reducción) of white
areas near the poles known as polar caps(gorras, tapones, fundas).
These polar caps may be composed of ordinary ice or of dry ice (frozen
carbon dioxide) and are thought to be(se piensa que son)
only a few inches thick. During the Martian summer the polar cap in that
hemisphere shrinks and the dark regions grow darker; in winter the polar cap
grows again and the dark regions become paler(más pálidos).
Satellites of Mars
Mars has two natural satellites, discovered by Asaph Hall in 1877. The
innermost(el más interior) of these, Phobos, is
about 7 mi (11 km) in diameter and orbits the planet with a period far less
than Mars's period of rotation (7 hr 39 min), causing it to rise(levantarse,
surgir, aparecer) in the west and set in the east. The outer
satellite, Deimos, is about 4 mi (6 km) in diameter. |
Inglés
|
Francés |
Alemán
|
Italiano |
Otros
1 (A-E)
| 2 (F-L) |
3 (N-S)
| 4 (T-U)
Árabe |
Chino |
Esperanto
|
Griego
|
Japonés
|
Portugués
|
Rumano
|
Ruso
|
Catalán
|
Euskera