{"id":1130,"date":"2004-11-15T15:52:00","date_gmt":"2004-11-15T14:52:00","guid":{"rendered":"https:\/\/kids.esa.int\/threats_from_space\/"},"modified":"2026-10-08T00:36:20","modified_gmt":"2026-10-07T22:36:20","slug":"threats_from_space","status":"publish","type":"post","link":"https:\/\/kids.esa.int\/fi\/threats_from_space\/","title":{"rendered":"Avaruudesta tulevat uhat"},"content":{"rendered":"
\n

Maa on aurinkokuntamme nelj\u00e4st\u00e4 kiviplaneetasta suurin. Se on kokonsa suhteen eritt\u00e4in painava. Sen ytimess\u00e4 on suuri, rautapitoinen ydin, jonka l\u00e4mp\u00f6tila nousee 6 000 asteeseen \u2013 yht\u00e4 kuuma kuin Auringon pinta.<\/p>\n<\/div>\n

Nestem\u00e4inen ulompi ydin py\u00f6rii planeetan py\u00f6rimisen mukana ja toimii kuin polkupy\u00f6r\u00e4n dynamo. T\u00e4m\u00e4n dynamon ansiosta Maa k\u00e4ytt\u00e4ytyy kuin voimakas magneetti.<\/p>\n

Maapallon magneettikentt\u00e4 muodostaa planeetan ymp\u00e4rille n\u00e4kym\u00e4tt\u00f6m\u00e4n kuplan ja toimii suojakilpen\u00e4. Se suojaa planeettaa suurimmalta osin niist\u00e4 suurinopeuksisista hiukkasista, joita aurinkomyrskyt sinkoavat avaruuteen. Toisinaan hiukkaset l\u00e4p\u00e4isev\u00e4t t\u00e4m\u00e4n esteen magneettisten napojen l\u00e4heisyydess\u00e4. T\u00e4m\u00e4 aiheuttaa maapallon revontulet \u2013 jotka tunnetaan yleisesti nimill\u00e4 pohjois- ja etel\u00e4nvalot.<\/p>\n

Maapallon pintaa suojaa my\u00f6s paksu ilmakeh\u00e4. Se est\u00e4\u00e4 suurimman osan avaruudesta tulevasta haitallisesta s\u00e4teilyst\u00e4. Se my\u00f6s saa pienet avaruudesta saapuvat kappaleet palamaan ilmi\u00f6n\u00e4, jota kutsutaan t\u00e4hdenlennoksi. Vain suuremmat meteoriitit ja komeetat p\u00e4\u00e4sev\u00e4t maan pinnalle ja r\u00e4j\u00e4ht\u00e4v\u00e4t siell\u00e4 j\u00e4tt\u00e4en j\u00e4lkeens\u00e4 suuria kraattereita.<\/p>\n

Toisin kuin Kuussa ja muissa kivisiss\u00e4 planeetoissa, Maassa on nyky\u00e4\u00e4n vain v\u00e4h\u00e4n t\u00f6rm\u00e4yskraattereita. Suurin osa niist\u00e4 on kulunut pois tai t\u00e4yttynyt virtaavan veden, tuulen ja j\u00e4\u00e4n vaikutuksesta.<\/p>","protected":false},"excerpt":{"rendered":"

Earth is the largest of the four rocky planets in our Solar System. It is very heavy for its size. At its centre is a large, iron-rich core, where 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\/2004\/05\/meteor_crater_in_arizona3\/17895645-2-eng-GB\/Meteor_Crater_in_Arizona.jpg","esa_banner_description":"Meteor Crater in Arizona","esa_banner_credit":"David Roddy, USGS","esa_banner_licence":"No ESA licences available","esa_banner_detail_url":"https:\/\/www.esa.int\/ESA_Multimedia\/Images\/2004\/05\/Meteor_Crater_in_Arizona3","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":[10,11,12],"tags":[2],"panel":[],"language":[],"age":[],"duration":[],"resource_type":[],"audience":[],"wf_post_folders":[],"class_list":["post-1130","post","type-post","status-publish","format-standard","hentry","category-learn","category-our-universe","category-planets-and-moons","tag-background-article"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/1130","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=1130"}],"version-history":[{"count":1,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/1130\/revisions"}],"predecessor-version":[{"id":2273,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/1130\/revisions\/2273"}],"wp:attachment":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/media?parent=1130"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/categories?post=1130"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/tags?post=1130"},{"taxonomy":"panel","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/panel?post=1130"},{"taxonomy":"language","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/language?post=1130"},{"taxonomy":"age","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/age?post=1130"},{"taxonomy":"duration","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/duration?post=1130"},{"taxonomy":"resource_type","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/resource_type?post=1130"},{"taxonomy":"audience","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/audience?post=1130"},{"taxonomy":"wf_post_folders","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/wf_post_folders?post=1130"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}