赤道(dao)(dao)脊(ji)是土(tu)星(xing)(xing)衛(wei)(wei)(wei)星(xing)(xing)上存在(zai)(zai)的(de)(de)一種(zhong)地貌特(te)征(zheng),至今已在(zai)(zai)三顆(ke)土(tu)星(xing)(xing)衛(wei)(wei)(wei)星(xing)(xing)的(de)(de)發現(xian)(xian)了該地貌——即較大的(de)(de)土(tu)衛(wei)(wei)(wei)八(ba)和較小的(de)(de)土(tu)衛(wei)(wei)(wei)十五、土(tu)衛(wei)(wei)(wei)十八(ba)。三顆(ke)衛(wei)(wei)(wei)星(xing)(xing)上的(de)(de)赤道(dao)(dao)脊(ji)所(suo)在(zai)(zai)位置都接近(jin)于衛(wei)(wei)(wei)星(xing)(xing)赤道(dao)(dao)。這種(zhong)地貌只存在(zai)(zai)于土(tu)星(xing)(xing)衛(wei)(wei)(wei)星(xing)(xing)上,但(dan)還不確定其形成是否有共同原因或者只是一種(zhong)巧合。三顆(ke)衛(wei)(wei)(wei)星(xing)(xing)上的(de)(de)赤道(dao)(dao)脊(ji)都是于2005年為卡西尼號所(suo)發現(xian)(xian)。
土(tu)(tu)衛(wei)八上的(de)赤(chi)道(dao)(dao)脊(ji)的(de)寬(kuan)達20公里(li),高達13公里(li),長度達1300公里(li)。土(tu)(tu)衛(wei)十(shi)(shi)五(wu)較之土(tu)(tu)衛(wei)八小得多(duo),但(dan)是按比例來說,其上的(de)赤(chi)道(dao)(dao)脊(ji)則更為(wei)顯眼(yan),該地形使得土(tu)(tu)衛(wei)十(shi)(shi)五(wu)的(de)形狀十(shi)(shi)分怪異(yi),看起(qi)來就像不明(ming)飛(fei)行物。土(tu)(tu)衛(wei)十(shi)(shi)八的(de)圖(tu)像較為(wei)模糊,但(dan)是仍能分辨出(chu)類似于土(tu)(tu)衛(wei)十(shi)(shi)八的(de)結構。
至今(jin)仍不清楚這(zhe)(zhe)些山脊(ji)是如何形(xing)(xing)成(cheng)(cheng)的(de)(de)(de)(de)(de),以及三(san)顆(ke)衛(wei)(wei)(wei)(wei)星(xing)(xing)(xing)上(shang)的(de)(de)(de)(de)(de)類似地形(xing)(xing)是否存在著某(mou)種(zhong)聯(lian)系(xi)。由(you)于(yu)(yu)土(tu)(tu)(tu)衛(wei)(wei)(wei)(wei)十五(wu)和土(tu)(tu)(tu)衛(wei)(wei)(wei)(wei)十八(ba)(ba)(ba)的(de)(de)(de)(de)(de)軌(gui)(gui)道(dao)(dao)(dao)位(wei)(wei)于(yu)(yu)土(tu)(tu)(tu)星(xing)(xing)(xing)環(huan)之內,因(yin)此(ci)有(you)人認為這(zhe)(zhe)兩顆(ke)衛(wei)(wei)(wei)(wei)星(xing)(xing)(xing)吸附了(le)(le)土(tu)(tu)(tu)星(xing)(xing)(xing)環(huan)中的(de)(de)(de)(de)(de)物質,從而(er)(er)在赤道(dao)(dao)(dao)處形(xing)(xing)成(cheng)(cheng)了(le)(le)這(zhe)(zhe)種(zhong)山脊(ji)。但是這(zhe)(zhe)種(zhong)理論并不適用于(yu)(yu)土(tu)(tu)(tu)衛(wei)(wei)(wei)(wei)八(ba)(ba)(ba),因(yin)為該衛(wei)(wei)(wei)(wei)星(xing)(xing)(xing)的(de)(de)(de)(de)(de)軌(gui)(gui)道(dao)(dao)(dao)位(wei)(wei)于(yu)(yu)土(tu)(tu)(tu)星(xing)(xing)(xing)環(huan)之外(wai)。曾有(you)科學家認為土(tu)(tu)(tu)衛(wei)(wei)(wei)(wei)八(ba)(ba)(ba)曾經位(wei)(wei)于(yu)(yu)土(tu)(tu)(tu)星(xing)(xing)(xing)環(huan)之內,從而(er)(er)形(xing)(xing)成(cheng)(cheng)了(le)(le)該地形(xing)(xing),后來由(you)于(yu)(yu)某(mou)種(zhong)未(wei)知(zhi)原因(yin)而(er)(er)被推出(chu)至現(xian)今(jin)的(de)(de)(de)(de)(de)位(wei)(wei)置(zhi)。與之對應,還有(you)一(yi)種(zhong)觀(guan)點(dian)(dian)認為土(tu)(tu)(tu)衛(wei)(wei)(wei)(wei)八(ba)(ba)(ba)的(de)(de)(de)(de)(de)軌(gui)(gui)道(dao)(dao)(dao)位(wei)(wei)置(zhi)并未(wei)發(fa)生(sheng)變化,而(er)(er)是土(tu)(tu)(tu)星(xing)(xing)(xing)環(huan)由(you)于(yu)(yu)土(tu)(tu)(tu)星(xing)(xing)(xing)的(de)(de)(de)(de)(de)重(zhong)力場而(er)(er)被拉(la)至更近的(de)(de)(de)(de)(de)軌(gui)(gui)道(dao)(dao)(dao)位(wei)(wei)置(zhi)。但是大多(duo)數(shu)科學家都傾(qing)向于(yu)(yu)以下觀(guan)點(dian)(dian):土(tu)(tu)(tu)衛(wei)(wei)(wei)(wei)八(ba)(ba)(ba)的(de)(de)(de)(de)(de)赤道(dao)(dao)(dao)脊(ji)是由(you)某(mou)種(zhong)內源性構造活動(dong)形(xing)(xing)成(cheng)(cheng)的(de)(de)(de)(de)(de),而(er)(er)與土(tu)(tu)(tu)衛(wei)(wei)(wei)(wei)十五(wu)和土(tu)(tu)(tu)衛(wei)(wei)(wei)(wei)十八(ba)(ba)(ba)的(de)(de)(de)(de)(de)赤道(dao)(dao)(dao)脊(ji)的(de)(de)(de)(de)(de)形(xing)(xing)成(cheng)(cheng)過程(cheng)沒有(you)聯(lian)系(xi)。