赤(chi)道(dao)脊是(shi)土(tu)星(xing)(xing)衛(wei)(wei)星(xing)(xing)上存(cun)在的(de)一種(zhong)地(di)貌特征,至今已在三顆(ke)土(tu)星(xing)(xing)衛(wei)(wei)星(xing)(xing)的(de)發現了(le)該地(di)貌——即(ji)較(jiao)大的(de)土(tu)衛(wei)(wei)八和較(jiao)小的(de)土(tu)衛(wei)(wei)十五、土(tu)衛(wei)(wei)十八。三顆(ke)衛(wei)(wei)星(xing)(xing)上的(de)赤(chi)道(dao)脊所在位置都接近于衛(wei)(wei)星(xing)(xing)赤(chi)道(dao)。這種(zhong)地(di)貌只存(cun)在于土(tu)星(xing)(xing)衛(wei)(wei)星(xing)(xing)上,但(dan)還(huan)不確定其形成是(shi)否(fou)有共同原因或者只是(shi)一種(zhong)巧合。三顆(ke)衛(wei)(wei)星(xing)(xing)上的(de)赤(chi)道(dao)脊都是(shi)于2005年為卡西尼號所發現。
土衛(wei)(wei)八(ba)上(shang)的(de)赤道(dao)脊(ji)的(de)寬達(da)20公(gong)里,高達(da)13公(gong)里,長度達(da)1300公(gong)里。土衛(wei)(wei)十(shi)五(wu)較之土衛(wei)(wei)八(ba)小(xiao)得(de)多,但是按比例來說,其上(shang)的(de)赤道(dao)脊(ji)則更為顯眼,該地(di)形使得(de)土衛(wei)(wei)十(shi)五(wu)的(de)形狀十(shi)分(fen)怪(guai)異,看起(qi)來就像不明飛行物。土衛(wei)(wei)十(shi)八(ba)的(de)圖像較為模糊(hu),但是仍能分(fen)辨出類似于土衛(wei)(wei)十(shi)八(ba)的(de)結構。
至(zhi)(zhi)今仍不(bu)清(qing)楚這(zhe)些(xie)山(shan)脊(ji)是(shi)如何形(xing)成的(de)(de),以及三顆(ke)衛(wei)星(xing)(xing)(xing)上的(de)(de)類似地(di)形(xing)是(shi)否存在(zai)著某(mou)種聯系。由(you)(you)于土(tu)(tu)衛(wei)十(shi)五(wu)和(he)(he)土(tu)(tu)衛(wei)十(shi)八(ba)(ba)的(de)(de)軌(gui)(gui)道(dao)(dao)(dao)位(wei)(wei)于土(tu)(tu)星(xing)(xing)(xing)環(huan)之內(nei),因(yin)(yin)此有(you)人認為(wei)這(zhe)兩顆(ke)衛(wei)星(xing)(xing)(xing)吸附了土(tu)(tu)星(xing)(xing)(xing)環(huan)中的(de)(de)物質(zhi),從而在(zai)赤道(dao)(dao)(dao)處(chu)形(xing)成了這(zhe)種山(shan)脊(ji)。但(dan)(dan)是(shi)這(zhe)種理(li)論并(bing)不(bu)適用于土(tu)(tu)衛(wei)八(ba)(ba),因(yin)(yin)為(wei)該衛(wei)星(xing)(xing)(xing)的(de)(de)軌(gui)(gui)道(dao)(dao)(dao)位(wei)(wei)于土(tu)(tu)星(xing)(xing)(xing)環(huan)之外。曾有(you)科學家(jia)(jia)認為(wei)土(tu)(tu)衛(wei)八(ba)(ba)曾經位(wei)(wei)于土(tu)(tu)星(xing)(xing)(xing)環(huan)之內(nei),從而形(xing)成了該地(di)形(xing),后(hou)來由(you)(you)于某(mou)種未知原因(yin)(yin)而被(bei)推出至(zhi)(zhi)現今的(de)(de)位(wei)(wei)置。與(yu)之對應,還有(you)一種觀(guan)點認為(wei)土(tu)(tu)衛(wei)八(ba)(ba)的(de)(de)軌(gui)(gui)道(dao)(dao)(dao)位(wei)(wei)置并(bing)未發生變化(hua),而是(shi)土(tu)(tu)星(xing)(xing)(xing)環(huan)由(you)(you)于土(tu)(tu)星(xing)(xing)(xing)的(de)(de)重力(li)場而被(bei)拉至(zhi)(zhi)更近的(de)(de)軌(gui)(gui)道(dao)(dao)(dao)位(wei)(wei)置。但(dan)(dan)是(shi)大多數科學家(jia)(jia)都(dou)傾向(xiang)于以下(xia)觀(guan)點:土(tu)(tu)衛(wei)八(ba)(ba)的(de)(de)赤道(dao)(dao)(dao)脊(ji)是(shi)由(you)(you)某(mou)種內(nei)源(yuan)性構(gou)造活動形(xing)成的(de)(de),而與(yu)土(tu)(tu)衛(wei)十(shi)五(wu)和(he)(he)土(tu)(tu)衛(wei)十(shi)八(ba)(ba)的(de)(de)赤道(dao)(dao)(dao)脊(ji)的(de)(de)形(xing)成過(guo)程沒有(you)聯系。