Pengguna:Mika.flowisch/Gempa Mars

Ilustrasi zona bayangan gelombang-P Bumi. Gelombang-S tidak menembus inti luar

Gempa Mars adalah fenomena gempa yang berasal dari getaran permukaan atau interior Mars. Fenomena ini terjadi karena pelepasan energi tiba-tiba akibat lempeng tektonik atau kemungkinan berasal dari wilayah seperti Olympus Mons atau Tharsis Montes. Deteksi dan analisis gempa di Mars akan meningkatkan pengetahuan mengenai struktur interior Mars serta membantu menentukan tingkat keaktifan gunung berapi Mars.

Gempa di bulan telah lama sudah diobservasi dan sudah terdokumentasi dengan lengkap. Selain itu, ada bukti bahwa Venus pernah mengalami gempa. Namun, gempa Mars baru diobservasi secara pasti pada 2019. Terdapat bukti yang menyakinkan mengenai Mars yang dahulu lebih aktif secara seismik yaitu terdapat garis magnet yang tersebar di wilayah yang luas di selatan Mars. Garis magnet di Bumi adalah tanda bahwa wilayah tersebut merupakan wilayah dengan kerak yang tipis dan dengan lambat melebar membentuk daratan baru. with clear magnetic striping over a large region of southern Mars. Magnetic striping on Earth is often a sign of a region of particularly thin crust splitting and spreading, forming new land in the slowly separating rifts; a prime example of this being the Mid-Atlantic Ridge. However, no clear spreading ridge has been found in this region, suggesting that another, possibly non-seismic explanation may be needed.

The 4.000 km (2.500 mi) long canyon system, Valles Marineris, has been suggested to be the remnant of an ancient Martian strike-slip fault. However, even if it was at some point an active fault, it is unknown whether the fault is still active, or if it has "frozen" into place.

Detectability

Cutaway illustration showing InSight's seismometer underneath the white windshield

The first attempts to detect seismic activity on Mars was with the Viking program in 1975, and although the landers were operated for several years, the seismographs were mounted on top of the landers and were unable to detect any clear seismic activity, due to the Martian wind blowing them too much. It was possible to rule out frequent and large marsquakes at that time. The Viking 2 device collected data for 2100 hours (89 days) of data over 560 sols of lander runtime. The Viking 1 lander did not return any data due to a problem activating the seismometer. Times when the windspeed was low at the Viking 2 site, allowed limits to be placed on seismic activity at the time and place on Mars.

Mars - InSight Lander - Seismometer (Sol 110)

There was one candidate for a Mars quake on Sol 80 by the Viking 2 seismometer. However, there was no wind speed data, so it's not possible to say whether it was the wind or not. Much of data set has been converted to ASCII files from the original recordings. Thirty years later, data from the InSight mission led to an increased interest in the Viking data set, and further analysis may reveal one of the largest collection of Mars dust devil detections.

The InSight Mars lander, launched in May 2018, landed on Mars on 26 November 2018 and deployed a seismometer called Seismic Experiment for Interior Structure (SEIS) on 19 December 2018 to search for marsquakes and analyze Mars's internal structure. Even if no seismic events are detected, the seismometer is expected to be sensitive enough to detect possibly several dozen meteors causing airbursts in Mars's atmosphere per year, as well as meteorite impacts. It will also investigate how the Martian crust and mantle respond to the effects of meteorite impacts, which gives clues to the planet's inner structure.

A faint seismic signal, believed to be a small marsquake, was measured and recorded by the InSight lander on 6 April 2019. The lander's seismometer detected ground vibrations while three distinct kinds of sounds were recorded, according to NASA. Three other events were recorded on 14 March, 10 April, and 11 April, but these signals were even smaller and more ambiguous in origin, making it difficult to determine their cause.

Mars - Seismic wave simulation (artist concept; 2019)

Mars - InSight Lander - Seismic Event (AudioVideoFile; Sol 128; 6 April 2019)

Candidate seismic events

Despite the drawbacks of significant wind interference, on Sol 80 of the Viking 2 lander's mission (roughly November 23, 1976), the on-board seismometer detected an unusual acceleration event during a period of relatively low wind speed. Based on the features of the signal and assuming Mars's crust behaves similar to Earth's crust near the lander's testing site in Southern California, the event was estimated to have a magnitude of 2.7 and a distance of roughly 110 kilometers. However, the wind speed was only measured 20 minutes previously, and 45 minutes after, at 2.6 and 3.6 meters per second, respectively. While a sudden wind gust of 16 m/s would have been required to produce the event, it cannot be completely ruled out.

On Sol 128 of the InSight lander mission the Seismic Experiment for Interior Structure (SEIS) detected one magnitude 1-2 seismic event on April 6. Three other unconfirmed candidate seismic events were detected on March 14, April 10 and April 11. The quake is similar to moonquakes detected during the Apollo program. It could have been caused by activity internal to the planet or by a meteorite striking the surface. The epicenter was believed to be within 100 km of the lander. As of 30 September 2019, SEIS had reported 450 events of various types.

See also

• Seismic Experiment for Interior Structure (SEIS, instrument on InSight Mars lander)
• Tectonics of Mars
• Volcanology of Mars

External links

• Video (2:48) – MarsQuakes di YouTube NASA (19 July 2019)