DALILIN DA YA SA WATA KE DAƊEWA YANA AMO

Idan raƙumin girgizar ƙasa ya ratsa Wata, siginar ba ta ƙarewa idan raƙumin ya wuce. Wata doguwar wutsiyar girgiza tana biye da shi, wato coda, wadda a kan Wata za ta iya ɗaukar har zuwa sa’o’i — kusan sau goma fiye da bayan girgizar ƙasa mai irin wannan ƙarfi (magnitude). Ga masana girgizar ƙasa (seismologists), wannan amo matsala ce: yana nutsar da raunanan amsa-kuwwa daga zurfafan layuka waɗanda za su bayyana cikin Wata.

Bayanin da aka saba bayarwa shi ne watsuwa mai ƙarfi (strong scattering) a cikin ɓawo mai ci gaba amma mai rashin daidaito sosai, inda raƙuman ke ƙara sauri da rage gudu daga wuri zuwa wuri. Amma kwaikwayon da aka gina a kan wannan ra’ayi ba su taɓa yin daidai da bayanan na’urorin auna girgizar ƙasa na Apollo ba, ko da da bambance-bambance masu ƙarfin da ba zai yiwu a zahiri ba.

Tsagogin da ba sa warkewa

Lei Zhang, Jinhai Zhang da abokan aiki a Chinese Academy of Sciences da China University of Geosciences sun bi wata hanya dabam. Ɓawon Wata cike yake da tsagogi (fractures): biliyoyin shekaru na faɗowar abubuwa (impacts), ƙanƙancewar Wata yayin da yake hucewa, tides (jan nauyi) da ayyukan dutsen wuta (volcanic activity) duk sun farfasa shi. A Duniya, ruwa-ruwa (fluids) a hankali suna warkar da irin waɗannan tsagogi. A kan Wata, babu ruwa, don haka suna nan a buɗe — gibba marasa komai a cikin dutse.

Tsagewa marar komai bango ce ga raƙumin girgizar ƙasa: babu abin da ke ratsawa ta cikinta. Raƙumin yana tunkuɗuwa gaba ɗaya (totally reflected). Da tsagewa ɗaya, wani ɓangare na fuskar raƙumin (wavefront) yana dawowa baya yayin da sauran ke ci gaba ba tare da damuwa ba. Da tsagogi da yawa, fuskar raƙumin tana farfashewa kuma tana zama a kulle, tana tunkuɗuwa daga tsagewa zuwa tsagewa, kuma makamashinta yana zubewa a hankali. A cewar marubutan, ba a taɓa la’akari da tasirin irin waɗannan tsagogi a kan raƙuman girgizar ƙasa na Wata ba a da.

Sake kunna faɗowar Apollo

Don gwada ra’ayin, ƙungiyar ta gina yanki mai fuska biyu (two-dimensional) na ɓawon Wata, mai tsawon kilomita 1,000 da zurfin kilomita 80, da tsagogi marasa komai a warwatse cikin dutse wanda in ban da su iri ɗaya ne ko’ina. Sun kwatanta hasashensa da bayanai 13 na Apollo na faɗowar wucin gadi (artificial impacts): matakan roka da suka gama aiki da matakan tashi na kumbunan saukar Wata (lunar-module ascent stages) da aka faɗo da su da gangan a kan Wata, waɗanda aka san lokaci da wurin faɗowarsu daidai. Tashoshin suna nesa da digiri 2.2 zuwa 28 na baka (arc).

Maimakon kaɗawa guda-guda, sun kwatanta ambulan (envelope) gaba ɗaya na kowane bayani — hawa a hankali, ƙoli mai faɗi, raguwa a hankali da ke sa ya yi kama da mazari (spindle).

Kilomita na farko ne ke yin aikin

• Da tsagogi da aka tattara a kilomita na sama, ambulan na kwaikwayo sun yi daidai da bayanai biyu na wakilci (representative) da alaƙa (correlations) ta 0.90 da 0.92. Ɓawo marar tsagogi yana ba da 0.56 da 0.47 kawai.
• Sauye-sauye goma sha biyu (variants) sun nuna daidai inda tsagogin ke da muhimmanci. Tsagogin da suka kai zurfin kilomita 12 sun yi daidai kamar tsagogin da aka taƙaita a kilomita na sama. Amma ka cire tsagogin daga wannan kilomita na sama, sai alaƙar ta faɗi zuwa 0.4–0.5.
• Tsawon tsagewa ma yana da muhimmanci: kilomita 0.5 zuwa 2 yana ba da alaƙa kusan 0.85, kilomita 4 kuma kusan 0.64 kawai. Mai yiwuwa tsagogin suna da tsawon kilomita 2 ko ƙasa da haka.
• Yawan tsagogi mai ɗan girma ne kaɗai ke sake samar da siffar coda da kuma saurin dusashewarta: kilomita na sama yana cike da tsagogi sosai.

A samfurin ma’auni (reference model), tsagogi 85, kowanne mai tsawon kilomita ɗaya da faɗin mita 250, an baza su a cikin kilomita na sama na yankin.

Kayan aiki ga abin da ke tafe

Radar a kan motocin binciken Wata (lunar rovers) ta binciki layuka har zuwa ’yan mita ɗari kaɗan, yawanci ƙasa da 500. Sakamakon girgizar ƙasa yana kaiwa zurfi fiye da haka, kusan kilomita ɗaya, kuma yana haɗa radar, taswirorin nauyi (gravity maps) da ma’aunai a kan samfuran da aka dawo da su.

Ana kuma iya juya samfurin: da zarar an san tsagogin, za a iya lissafa amonsu a cire shi daga bayanan, don raunanan amsa-kuwwa daga cikin zurfin Wata su bayyana. Na’urorin auna girgizar ƙasa na nan gaba — a kan Chang’e-7, kusa da Kudancin Wata (south pole) tare da Artemis, da kuma a ɗaya gefen Wata (far side) — za su iya gwada shi. Kuma ayyukan da ke fatan gano raƙuman nauyi (gravitational waves) ta hanyar sauraron Wata na iya zama dole su yi la’akari da waɗannan tsagogi.

Samfurin har yanzu sauƙaƙawa ne: yanki mai fuska biyu, dutse iri ɗaya a kewayen tsagogin. Tsagogi na gaske masu fuska uku ne, suna ratsa juna, kuma suna cikin ɓawo wanda shi ma ba daidai yake ba. Amma ko wannan sigar mara ado tana yin amo kamar Wata.