{"id":1142,"date":"2004-11-19T08:27:00","date_gmt":"2004-11-19T07:27:00","guid":{"rendered":"https:\/\/kids.esa.int\/are_we_alone_life_on_earth\/"},"modified":"2026-10-08T00:36:29","modified_gmt":"2026-10-07T22:36:29","slug":"are_we_alone_life_on_earth","status":"publish","type":"post","link":"https:\/\/kids.esa.int\/fi\/are_we_alone_life_on_earth\/","title":{"rendered":"El\u00e4m\u00e4 maapallolla"},"content":{"rendered":"
\n

Kukaan ei tied\u00e4, miten tai miksi el\u00e4m\u00e4 sai alkunsa. Tied\u00e4mme kuitenkin, ett\u00e4 el\u00e4m\u00e4 Maassa alkoi v\u00e4hint\u00e4\u00e4n 3,8 miljardia (3 800 000 000) vuotta sitten. Tuolloin nuori planeetta oli jo j\u00e4\u00e4htynyt ja muodostanut kivisen kuoren. Jotkut tutkijat uskovat, ett\u00e4 el\u00e4m\u00e4 sai alkunsa kallioaltaassa tai meress\u00e4. Toiset taas ajattelevat, ett\u00e4 se saattoi saapua avaruudesta komeettojen ja asteroidien mukana.<\/p>\n<\/div>\n

Tiet\u00e4\u00e4ksemme Maa on ainoa paikka, josta on l\u00f6ydetty el\u00e4m\u00e4\u00e4. Minne tahansa katsommekin planeetallamme, bakteerit ja muut yksinkertaiset el\u00e4m\u00e4nmuodot ovat l\u00f6yt\u00e4neet sielt\u00e4 kotinsa.<\/p>\n

Kasvit ja el\u00e4imet tarvitsevat auringonvaloa kasvaakseen. 1970-luvulle asti tutkijat uskoivat, ett\u00e4 el\u00e4m\u00e4\u00e4 oli olemassa vain l\u00e4hell\u00e4 maapallon pintaa.<\/p>\n

\"Mars
Mars 5,5 miljoonan kilometrin et\u00e4isyydelt\u00e4, kuvattu 1. joulukuuta<\/figcaption><\/figure>\n

Siit\u00e4 l\u00e4htien bakteereja on l\u00f6ydetty useiden kilometrien syvyydest\u00e4 maan alla kiinte\u00e4n kiven sis\u00e4lt\u00e4. Ne el\u00e4v\u00e4t kiven sis\u00e4lt\u00e4mist\u00e4 kaasuista ja mineraaleista. Bakteereja on l\u00f6ydetty my\u00f6s vahvoista hapoista, Antarktiksen pakkasessa sek\u00e4 meren pimeiss\u00e4 syvyyksiss\u00e4 sijaitsevien kuumien l\u00e4hteiden l\u00e4heisyydest\u00e4. Jotkut pystyv\u00e4t selviytym\u00e4\u00e4n jopa eritt\u00e4in radioaktiivisissa paikoissa. Niin kauan kuin vett\u00e4 on saatavilla, el\u00e4m\u00e4 pystyy saamaan jalansijaa.<\/p>\n

Jos el\u00e4m\u00e4 on niin vaikeaa, voisiko se synty\u00e4 ja s\u00e4ily\u00e4 muilla planeetoilla? Aurinkokuntamme todenn\u00e4k\u00f6isin paikka on Mars.<\/p>","protected":false},"excerpt":{"rendered":"

No one knows how or why life began. We do know that life on Earth started at least 3.8 billion (3 800 000 000) years ago. By this time, the […]<\/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\/2001\/07\/life_in_extreme_conditions_on_earth_raises_hopes_for_life_elsewhere_in_the_universe2\/17864454-3-eng-GB\/Life_in_extreme_conditions_on_Earth_raises_hopes_for_life_elsewhere_in_the_universe.jpg","esa_banner_description":"","esa_banner_credit":"ESA","esa_banner_licence":"ESA Standard Licence","esa_banner_detail_url":"https:\/\/www.esa.int\/ESA_Multimedia\/Images\/2001\/07\/Life_in_extreme_conditions_on_Earth_raises_hopes_for_life_elsewhere_in_the_universe2","esa_external_url":"","esa_external_new_window":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":true},"categories":[14,10,13],"tags":[2],"panel":[],"language":[],"age":[],"duration":[],"resource_type":[],"audience":[],"wf_post_folders":[],"class_list":["post-1142","post","type-post","status-publish","format-standard","hentry","category-are-we-alone","category-learn","category-life-in-space","tag-background-article"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/1142","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/comments?post=1142"}],"version-history":[{"count":4,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/1142\/revisions"}],"predecessor-version":[{"id":4868,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/1142\/revisions\/4868"}],"wp:attachment":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/media?parent=1142"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/categories?post=1142"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/tags?post=1142"},{"taxonomy":"panel","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/panel?post=1142"},{"taxonomy":"language","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/language?post=1142"},{"taxonomy":"age","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/age?post=1142"},{"taxonomy":"duration","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/duration?post=1142"},{"taxonomy":"resource_type","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/resource_type?post=1142"},{"taxonomy":"audience","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/audience?post=1142"},{"taxonomy":"wf_post_folders","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/wf_post_folders?post=1142"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}