{"id":982,"date":"2008-10-17T09:18:00","date_gmt":"2008-10-17T07:18:00","guid":{"rendered":"https:\/\/kids.esa.int\/solving_the_mysteries_of_a_martian_moon\/"},"modified":"2026-10-08T00:34:29","modified_gmt":"2026-10-07T22:34:29","slug":"solving_the_mysteries_of_a_martian_moon","status":"publish","type":"post","link":"https:\/\/kids.esa.int\/fi\/solving_the_mysteries_of_a_martian_moon\/","title":{"rendered":"Marsin kuun mysteerien selvitt\u00e4minen"},"content":{"rendered":"<div class=\"lede\">\n<p>Vuonna 1877 amerikkalainen t\u00e4htitieteilij\u00e4 Asaph Hall l\u00f6ysi kaksi pient\u00e4 kuuta, jotka kiert\u00e4v\u00e4t Mars-planeettaa. Ne nimettiin Phobosiksi (Pelko) ja Deimosiksi (Paniikki). Yli 130 vuotta my\u00f6hemmin tutkijat yritt\u00e4v\u00e4t yh\u00e4 selvitt\u00e4\u00e4 n\u00e4iden kuiden salaisuuksia. ESA:n Mars Express -avaruusluotaimen viimeaikaiset l\u00e4hilennot ovat kuitenkin antaneet vihjeit\u00e4 siit\u00e4, mist\u00e4 ne koostuvat ja mist\u00e4 ne ovat per\u00e4isin.<\/p>\n<\/div>\n<p>Mars Express on ainoa t\u00e4ll\u00e4 hetkell\u00e4 Punaisen planeetan ymp\u00e4rill\u00e4 toimiva avaruusalus, joka liikkuu eritt\u00e4in elliptisell\u00e4 (munanmuotoisella) kiertoradalla. T\u00e4m\u00e4 reitti vie sen Phoboksen kiertoradan yli, mink\u00e4 ansiosta se pystyy n\u00e4kem\u00e4\u00e4n pienen kuun kaikki puolet. (Aivan kuten Maan Kuu, my\u00f6s Phobos pit\u00e4\u00e4 aina saman puolen kohti l\u00e4heist\u00e4 planeettaa.) 23. hein\u00e4kuuta ja 15. syyskuuta 2008 v\u00e4lisen\u00e4 aikana Mars Express suoritti kahdeksan ohilentoa Phoboksen ohi, kulkien sen ohi et\u00e4isyyksill\u00e4, jotka vaihtelivat 4 500 kilometrist\u00e4 vain 93 kilometriin.<\/p>\n<figure class=\"wp-block-image size-natural\" data-width=\"400\" data-credit=\"ESA\/ DLR (K.Willner)\/ FU Berlin (G. Neukum)\" data-detail-url=\"https:\/\/www.esa.int\/Media\/Animations\/Phobos_animation_-_Image2_422-20081013-0000-6-mov-01-PhobosSeries\" data-licence=\"ESA Standard Licence\" data-licence-url=\"https:\/\/www.esa.int\/ESA_Multimedia\/Terms_and_conditions_of_use_of_images_and_videos_available_on_the_esa_website\"><img decoding=\"async\" loading=\"lazy\" style=\"max-width:100%;height:auto\" src=\"https:\/\/www.esa.int\/var\/esa\/storage\/images\/media\/animations\/phobos_animation_-_image2_422-20081013-0000-6-mov-01-phobosseries\/4172-5-eng-GB\/Phobos_animation_-_Image2_422-20081013-0000-6-mov-01-PhobosSeries.jpg\" alt=\"\"><\/figure>\n<p>L\u00e4hikuvat osoittavat, ett\u00e4 suurempi kuu, Phobos, on perunanmuotoinen avaruuskivi, jonka mitat ovat vain 27 km \u00d7 22 km \u00d7 19 km. Se on eritt\u00e4in tumma \u2013 mustempi kuin hiili \u2013 ja t\u00e4ynn\u00e4 kraattereita. Seuraamalla tarkasti, miten Phobos vet\u00e4\u00e4 Mars Expressi\u00e4 puoleensa jokaisen ohilennon aikana, tutkijat ovat havainneet, ett\u00e4 satelliitti ei ole kovin tihe\u00e4. Se on l\u00e4hes varmasti \u2018kivikasa\u2019 \u2013 joka koostuu monista kivenpalasista, joita painovoima pit\u00e4\u00e4 yhdess\u00e4 \u2013 eik\u00e4 yksitt\u00e4inen, kiinte\u00e4 kappale.<\/p>\n<p>Mars Expressin tutkimusten mukaan Phobos ja Deimos ovat saattaneet olla aikoinaan asteroideja, jotka kierteliv\u00e4t Aurinkoa Marsin ja Jupiterin v\u00e4liss\u00e4. Kukaan ei kuitenkaan viel\u00e4 osaa selitt\u00e4\u00e4, miten Mars vangitsi ne ja miten ne p\u00e4\u00e4tyiv\u00e4t \u2018normaaleille\u2019 kiertoradoille Marsin p\u00e4iv\u00e4ntasaajan yl\u00e4puolelle.<\/p>","protected":false},"excerpt":{"rendered":"<p>In 1877, the American astronomer Asaph Hall discovered two small moons circling the planet Mars. They were named Phobos (Fear) and Deimos (Panic). More than 130 years later, scientists are [&hellip;]<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"esa_banner_image":"https:\/\/www.esa.int\/var\/esa\/storage\/images\/esa_multimedia\/images\/2008\/10\/mars_moon_phobos2\/17879181-2-eng-GB\/Mars_moon_Phobos.jpg","esa_banner_description":"Mars\u2019 moon Phobos","esa_banner_credit":"ESA\/ DLR\/ FU Berlin (G. 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