赤(chi)(chi)道(dao)(dao)脊(ji)(ji)是(shi)土(tu)星(xing)(xing)(xing)衛(wei)(wei)(wei)(wei)(wei)星(xing)(xing)(xing)上存在的(de)(de)(de)一種地(di)貌(mao)特征,至今(jin)已在三(san)(san)(san)顆(ke)土(tu)星(xing)(xing)(xing)衛(wei)(wei)(wei)(wei)(wei)星(xing)(xing)(xing)的(de)(de)(de)發現了該地(di)貌(mao)——即(ji)較(jiao)大(da)的(de)(de)(de)土(tu)衛(wei)(wei)(wei)(wei)(wei)八(ba)和較(jiao)小的(de)(de)(de)土(tu)衛(wei)(wei)(wei)(wei)(wei)十五(wu)、土(tu)衛(wei)(wei)(wei)(wei)(wei)十八(ba)。三(san)(san)(san)顆(ke)衛(wei)(wei)(wei)(wei)(wei)星(xing)(xing)(xing)上的(de)(de)(de)赤(chi)(chi)道(dao)(dao)脊(ji)(ji)所(suo)在位置都(dou)接近于衛(wei)(wei)(wei)(wei)(wei)星(xing)(xing)(xing)赤(chi)(chi)道(dao)(dao)。這種地(di)貌(mao)只存在于土(tu)星(xing)(xing)(xing)衛(wei)(wei)(wei)(wei)(wei)星(xing)(xing)(xing)上,但還不(bu)確定其(qi)形成是(shi)否有共同原因或者只是(shi)一種巧合。三(san)(san)(san)顆(ke)衛(wei)(wei)(wei)(wei)(wei)星(xing)(xing)(xing)上的(de)(de)(de)赤(chi)(chi)道(dao)(dao)脊(ji)(ji)都(dou)是(shi)于2005年為卡西尼號所(suo)發現。
土衛八(ba)上的(de)赤道脊的(de)寬達(da)20公里(li),高(gao)達(da)13公里(li),長(chang)度達(da)1300公里(li)。土衛十(shi)五較之土衛八(ba)小(xiao)得(de)多,但是(shi)按比例(li)來(lai)說,其上的(de)赤道脊則更為顯眼(yan),該地形(xing)使得(de)土衛十(shi)五的(de)形(xing)狀十(shi)分怪異,看起來(lai)就像不明飛行物。土衛十(shi)八(ba)的(de)圖(tu)像較為模(mo)糊,但是(shi)仍(reng)能分辨出類似于土衛十(shi)八(ba)的(de)結構(gou)。
至今仍不清楚(chu)這(zhe)(zhe)些(xie)山(shan)脊(ji)是(shi)如何形(xing)(xing)成(cheng)(cheng)的(de)(de)(de),以(yi)及三顆(ke)衛(wei)(wei)(wei)星(xing)上(shang)的(de)(de)(de)類似(si)地形(xing)(xing)是(shi)否存在(zai)著某種(zhong)聯系(xi)(xi)。由(you)于(yu)(yu)(yu)土(tu)(tu)(tu)(tu)衛(wei)(wei)(wei)十(shi)五和土(tu)(tu)(tu)(tu)衛(wei)(wei)(wei)十(shi)八(ba)的(de)(de)(de)軌(gui)道(dao)位于(yu)(yu)(yu)土(tu)(tu)(tu)(tu)星(xing)環(huan)(huan)之內,因(yin)(yin)此有(you)(you)人認(ren)為這(zhe)(zhe)兩顆(ke)衛(wei)(wei)(wei)星(xing)吸附(fu)了土(tu)(tu)(tu)(tu)星(xing)環(huan)(huan)中的(de)(de)(de)物質,從而在(zai)赤道(dao)處(chu)形(xing)(xing)成(cheng)(cheng)了這(zhe)(zhe)種(zhong)山(shan)脊(ji)。但是(shi)這(zhe)(zhe)種(zhong)理論并不適(shi)用于(yu)(yu)(yu)土(tu)(tu)(tu)(tu)衛(wei)(wei)(wei)八(ba),因(yin)(yin)為該衛(wei)(wei)(wei)星(xing)的(de)(de)(de)軌(gui)道(dao)位于(yu)(yu)(yu)土(tu)(tu)(tu)(tu)星(xing)環(huan)(huan)之外。曾(ceng)(ceng)有(you)(you)科學家認(ren)為土(tu)(tu)(tu)(tu)衛(wei)(wei)(wei)八(ba)曾(ceng)(ceng)經位于(yu)(yu)(yu)土(tu)(tu)(tu)(tu)星(xing)環(huan)(huan)之內,從而形(xing)(xing)成(cheng)(cheng)了該地形(xing)(xing),后(hou)來由(you)于(yu)(yu)(yu)某種(zhong)未知原因(yin)(yin)而被推出至現今的(de)(de)(de)位置(zhi)。與之對應,還有(you)(you)一種(zhong)觀點認(ren)為土(tu)(tu)(tu)(tu)衛(wei)(wei)(wei)八(ba)的(de)(de)(de)軌(gui)道(dao)位置(zhi)并未發生(sheng)變化,而是(shi)土(tu)(tu)(tu)(tu)星(xing)環(huan)(huan)由(you)于(yu)(yu)(yu)土(tu)(tu)(tu)(tu)星(xing)的(de)(de)(de)重(zhong)力場而被拉(la)至更近的(de)(de)(de)軌(gui)道(dao)位置(zhi)。但是(shi)大(da)多數科學家都傾向(xiang)于(yu)(yu)(yu)以(yi)下觀點:土(tu)(tu)(tu)(tu)衛(wei)(wei)(wei)八(ba)的(de)(de)(de)赤道(dao)脊(ji)是(shi)由(you)某種(zhong)內源性構(gou)造活動形(xing)(xing)成(cheng)(cheng)的(de)(de)(de),而與土(tu)(tu)(tu)(tu)衛(wei)(wei)(wei)十(shi)五和土(tu)(tu)(tu)(tu)衛(wei)(wei)(wei)十(shi)八(ba)的(de)(de)(de)赤道(dao)脊(ji)的(de)(de)(de)形(xing)(xing)成(cheng)(cheng)過程沒有(you)(you)聯系(xi)(xi)。