Nyorera kupfuurira kweiyi ndima - Pamitambo yeOlympic yeZhizha ya2008 muBeijing, Jansen akawedzera purogiramu yake yekushambira kumitambo miviri: 200-metre freestyle uye 4 × 200-metre freestyle relay. Akachenesa FINA B-standard yekupinda nguva ye2: 02.20 (200 m freestyle) kubva kuDanish Open muCopenhagen. Mumakwikwi emamita mazana maviri akasununguka, Jansen akamhanya kusvika pachinzvimbo chechina uye makumi matatu nemana pakupedzisira pakurova kwakafanana neAtene nechikamu chimwe chete pamberi peSingapore Lynette Lim muna 2:01.30. Akashandawo pamwe chete naHjorth-Hansen, Micha Østergaard, naLotte Friis mu 4 × 200 m freestyle relay
. Achishambira muchikamu chechitatu, Jansen akarekodha kupatsanurwa kwe2: 00,31, uye timu yeDenmark yakapedza kupisa kwekutanga mune yegumi yakazara neDanish rekodhi ye8: 00.81.