2019 October 4

InSight on a Cloudy Day
Image Credit:
NASA, JPL-Caltech, Mars InSight

Explanation: Clouds drift through the sky as the light fades near sunset in this three frame animated gif. The scene was captured on sol 145 beginning around 6:30pm local time by a camera on the Mars InSight lander. Of course, InSight’s martian day, sol 145, corresponds to Earth calendar date April 25, 2019. Under the 69 centimeter (2.3 foot) diameter dome in the foreground is the lander’s sensitive seismometer SEIS designed to detect marsquakes. Earthquakes reveal internal structures on planet Earth, and so tremors detected by SEIS can explore beneath the martian surface. In particular, two typical marsquakes were recorded by SEIS on May 22 (sol 173) and July 25 (sol 235). The subtle tremors from the Red Planet are at very low frequencies though, and for listening have to be processed into the audio frequency range. In the sped up recordings external noises more prevalent on cool martian evenings and likely caused by mechanical shifts and contractions have been technically dubbed dinks and donks.

NASA, JPL-Caltech, Mars InSight

说明: 在这部三格gif动画里,随着日落时分天色逐渐暗去,乌也飘过天空。这幅由火星察号登陆器的相机拍摄之景观,摄影起点是第145星日的当地时间6:30pm。而洞察号的第145火星日(sol 145),对应的地球日是2019年4月25日。前景位在69公分圆形的罩子下,是登陆器用来侦测火星震的高灵敏地震仪。在地球上,地震可用来找出内部的结构,所以SEIS测到的震动,可用来探索火星次表面构造。具体来说,SEIS就在5月22日(sol 173)及7月25日(sol 235)记录到二例典型的火星震。这些源自火星的轻微震动频率很低,想听的话要把频率提高到声频。在这些慢录快播的音讯里,外部杂讯较常出现在火星夜晚时,所以其可能来源是仪器部件移位与缩收造成的叮叮当当声。

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