KHOA HOC
G
an den Tnmg Thu nam nay, bao chi ram rd dua tin: Tren Mat trang chd nao ciing cd nudc. Td Daily Mail (Thu tin hang ngay) ngay 25 thang 9 nam 2009 viet"... Ba phan tich rieng re diing du lieu tii ve tinh Chandrayaan-1 ciia An Do va hai tau vU tru ciia My la Cassini va Deep Impact Probe da tim thay bang chiing la cd nudc tren dat ciia Mat trang va chiing td la nudc trai rdng ra tren toan bd be mat ciia Mat trang...". Td Science (Khoa hgc) danh so dac biet ra ngay 24 thang 8 nam 2009 cdng bd van de nay.
Cd phai lau nay ngudi ta van cho la ehj HSng rat khd khan, nay mdi dot nggt phat hien ra la chi kha ucit at'.' Khdng phai nhu vay. Chj HSng da dugc tim hieu ky tir thdi mdi Igt Idng, cho den nhung nam gan day ngudi ta khdng ngan ngai tham dd den tan
chan ta ke tdc ciia chj. \ ^ trong nhung van de ly thii thi van de nudc dch j Hang la rat hap dan, nhung khong phai mcii la.
Ta cd the gid cac trang Wikipedia de lay mdt it dii lieu ve chj Hang, diem lai cac thuyet ndi ve chj HSng da sinh ra nhu the nao, de cuoi ciing xet rieng van de nudc d chj Hang thtrc te la cd den dau va tai sao bay gid rat dugc quan tam.
1 . M A T T R A N G - VE TINH C U A TRAI DAT
Mat trang la ve tinh tu nhien duy nhat cua Trai dat va la ve tinh tu nhien Icin thir nam trong He Mat trdi.
Khoang each trung binh tinh tir tam Trai dat den Mat trang la 384.403km, lein khoang 30 lan dudng kinh Trai dat. Ducing kinh Mat trang la 3474km, tiic la
1 2 K h o a h o c & T 6 q u 6 c thang 10 2009
han mdt phan tudirdng kinh Trai dat. Khoi liromg Mat trang khoang bSng 2% khoi lugng Trai d4t va luc hap dan d be mat Mat trang bdng 17%
luc hap dan tren be mat Trai ddt.
Mat trang quay mgt vdng quanh Trai dat vcii chu ky quy dao la 27,32 ngay, nhung do cd bien ddi djnh ky trong hinh hgc he Trai ddt - Mat trang - Mat trdi nen chu ky giao hdi ciia Mat trang la 29,53 ngay. Mat trang ndm tren quy dao quay ddng bd cd nghia la nd giii nguyen mdt mat hucing veTrai dat dtdt ca mgi thcii diem.
Chiing ta chi nhin thay mdt phia cua Mat trang.
Mat quay ve phia Trai dat dugc ggi la phdn nhin thay, phia ddi dien dugc ggi la phdn khdng nhin thay. Cd khi phan khdng nhin thay dd dugc ggi la phan tdi nhtmg thuc sir thi phdn nay van dugc mat tnii chieu sang theo chu ky tucmg tu nhu phan nhin thay. Khi trdi trong, trang sang mat thucing van nhin thay rd tren Mat trang cd viing sang vung sam. Cac nha thien van thcii cd ggi viing mau sam la mare, tieng Latinh cd nghTa la bie'n, vi ngudi xua cho dd la ncri chira day nudc. Cac viing cd mau sang tren Mat trang cae nha thien van cd ggi la terrae, tieng Latin nghTa la cao nguyen bcii chiing cao hem viing bien. Be mat Mat trang cho thay bdng chiing cd nhieu ho hinh thanh khi cac thien thach va sao chdi va cham vao be mat Mat trang. Tinh ra cd khoang nira trieu hd va cham vdi dudng kinh ldn hem 1 km. Vi khdng cd khi quyen, khdng bj anh hucing then tiet va khdng cd boat ddng dja chat manh nen cac hd va cham dugc bao tdn kha tdt so vdi cac hd va cham tren Trai dat.
Cac vung sam d be mat nhin thay, ma cac nha thien van cd ggi la bie'n, thuc ra la vimg triing Icin do va cham:
bie'n Imbrium, bien Serenitatiss, bie'n Crisium, bie'n Nectaris (sau nay ngirdi ta gpi la vimg trung chir khdng ggi la bie'n nira). Hd va cham Icin nhat tren Mat trang tao ra vimg trung ldn nhat ggi la viing trung nam cue Aitken. Vimg nay ndm d phia mat khdng nhin thay ciia Mat trang, dudng kinh den 2240km va sau khoang 13km. Bao triim phia ngoai be mat Mat trang la mdt Idp bui rat mjn dugc ggi la regolith. Dd la vat chdt vd vun ra thanh nhirng hat rat nhd do qua trinh va cham. Be mat nao d Mat trang hinh thanh mucin (be mat tre) thi cd Idp regolith mdng hon .so vdi be mat hinh thanh sdm (be mat gia). Tai cac vimg triing (be mat tre hinh thanh do va cham sau
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KHOA HOC
OtU Tf«ntr«»i««A/««r«»
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Ve tinh quy dgo Mat trang Chadragaan
nay) Icip regolith chi day khoang 3-5 met, d cac cao nguyen (be mat gia) Icip regolith day den 10-20 met.
Ben dircii liip regolith nay la cac Idp nen da dirt gay day den hang chuc kilomet.
2. MAT TRANG HINH THANH NHU THE NAO?
Can cir vao nhirng dir lieu thu thap dugc, nhieu gia thuyet da dugc dua ra ve su hinh thanh eiia Mat trang. Tat ca deu cho rang Mat trang hinh thanh tren 4 ty nam trudc day. Cd bdn gia thuyet hay dugc ndi den.
- Gia thuyet phan doi. Theo gia thuyet nay thi Mat trang da vd ra tir vo Trai dat do cac luc ly tam, de lai mdt viing triing dugc cho la Thai Binh Ducmg.
Nhung neu vay thi Trai dat liic Mat trang vang ra phai cd tdc do quay rat Icin va Mat trang tir luc vd ra dd phai quay theo mat xich dao qua dat. Thtrc te lai khdng phai nhu vay.
- Gia thuyet b a t giir. Theo gia thuyet nay Mat trang da dugc hinh thanh tir dau dd va cudi cung bj lire hap dan Trai dat bat giir. Tuy nhien mudn bat giir thi phai ed ca che sao cho Mat trang khi lai giin Trai dat chuyen ddng bj cham lai. Thi du nhu hi khi quyen Trai dat liic dd rat rdng, kim hiiin chuyen dcing ciia Mat trang den mot liic Mat triing bj luc hiip dan hiit va trd thanh vc tinh. Nhung khi quyen Trai diit rdng den the la vd ly va chua the tim dugc mcit ccr che nao kha dT lam cham chuyen ddng Mill trang.
- Gia thuyet cun}; hinh t h a n h . (iia tluuct niiy
thang 10 20(' K h o a h o c & TA q u 6 c
I KHOA HOC
Ho l&n a Nam cue ciia Mat trdng
cho rang Trai dat va Mat trang ciing hinh thanh d mdt thcM diem va d hai nai gan nhau. Qua trinh hinh thanh la qua trinh bdi tu cac hat nhd ciing nhu ldn ctia may vat chat vao thcri each day 4,6 ty nam, nhung tinh toan ty trpng cho thay Trai dat cd ty trgng 5,5 lan ti trgng ciia nudc cdn Mat trang cd ti trgng chi 3,3 lan. Neu bdi tu tir cimg mot may \ at chat each Mat trdi gan nhu nhau, tai sao ti trpng chenh lech nhau nhieu nhu vay?
Gia thuyet vu va cham ldn. Theo gia thuyet nay thi khi Trai dat ehua hoan toiin hinh thanh xong. cd mdt vat the to nhu sao Hoa va cham vao Trai dat, lam mdt lugng ldn vat chat tir Trai dat bj ban ra.
Lucyng \ at chat niiy chay theo quy dao ciia Trai dat, qua qua trinh bdi tu tao nen Mat trang. Nhieu phep phan tieh thiinh phan cac chat d Mat triing va d Trai dat. cac phep tinh md phdng cahgc cho thay gia thuyet nay la cd ly; tuy riing vat the to nhu sao Hoa la gi, d dau ra, va cham xong di dau v.v.. .den nay van chua dugc giai dap. Cac nhii khoa hpc hien nay ting hp manh giii thuyet \ u va cham ldn \a cang tim hieu sau thi cang thay gia thuyet nay dung.
3. MATTRANG D A D U Q C T I M HIEU NHU THE NAO
Cac nha thien \'an cd dii dimg mat thudng quan sat Mat trang va hinh dung tren dd cd bie'n ca, niii sdng, nen dii ditng tir bien (mare) va tir cao nguyen (ter- rae) di; chi \img siim, \img sang mat nhin thay duoc tren dd. Nhu vay, tir xua ngudi ta van nghT tren dd
cd ddy nudc. Budc tien ddu tien quan sat ky Mat trang la nhdcd kinh \ ten vgng. Galileo Galilei da quan sat dugc cac nggn niii va cac hd va cham d tren dd.
Nhimg chuang trinh Luna (Mat trang) ciia Lien Xo nam 1959 mdi la budc dot pha quan trgng: Luna 1 la vat the ddu tien thoat khdi lire hap dan Trai dat den gan Mat trang, Luna 2 la vat the nhan tao dau tien va cham be mat Mat trang va Luna 3 da chup anh dugc be mat khdng nhin thay ciia Mat trang.
Den nam 1966 Luna 9 ha canh nhe nhang xudng Mat trang va Luna 10 khdng ngucri lai bay quanh Mat Uang.
Tiep dd, cac mau vat Ui Mat frang da dugc Luna 16, Luna 20, Luna 24 lay dua ve Trai dat nghien ciiu.
My ciing phdng mdt loat tau Apollo lay mau Ui Mat trang dira ve Trai dat nghien ciiu. Thdi nhung nam 1960-19 70 viec tim hieu Mat trang dugc thiic day manh giua cac cucmg qudc do cd chien tranh lanh. Dinh cao ciia cudc chay dua len Mat trang la nam 1969;
hai phi hanh gia My la Neil Armstrong va Buzz Adrin thuc hien cudc dd bd ciia ngucii len Mat trang.
Budc chan ciia Neil Armstrong tren cai ggi la Bien Yen Lang (Sea of Tranquillity) diing khdng phai la ldi nudc ma la di tren da bazan.
Cac thiet bj tham dd, may do dja chan, may do Ui,
14 Khoa hoc & T6 qudc thang 10 2009
may phan tich... dugc dat d nhieu nai tren Mat trang, cung cap khdng biet ca man nao la so lieu do dac.
Viec nghien cim Mat trang cd mdt thdi bj ehiing lai, cd ve nhu de tap trung siic luc sang sao Hda, sao Kim va nhiing nai xa xdi hon. Nhung sau dd, nam 1990 Nhat Ban trd thanh nudc thii ba dua tau vu tni vao quy dao Mat trang, va nam 1994 My cung quay lai Mat trang vdi tau vu tru Clementine de lap ban do dja hinh gdn nhu toan bd Mat trang va chup Mat trang bdng nhieu loai phd. Tiep theo dd nam 1998 My phdng tau Lunar Prospector (Ngudi tham dd Mat trang) cd phd ke natron, ban dugc natron di sau vao cac Icip phia dudi, phan tich phd tan xa nguge lai, biet dugc d nhirng Idp sau phia dudi cd hydrd hay khdng. Nam 2008 My phdng Lunar Recormaissance Orbiter LRO (Tau quy dao trinh sat Mat trang), ndi bat la ed nhung cam bien rat tien tien cd the nhan biet dugc la cd nudc hay khdng theo
KHOA HOC I bdn phuemg phap khac nhau, nham dua ra ket luan cuoi cung la Mat trang cd nudc hay khdng. Thang 2 nam 2008 An Dp eiing phdng tau xU tru khdng ngucri lai Chandrayaan 1 tham dd Mat trang. Trung Qudc ciing da phdng tau Thucing Nga 1 vao cudi nam 2007 chuyen tham hiem Mat trang (Thucing Nga cd nghTa nhu Hang Nga tiic chj Hang).
Nam 2007, Nhat Ban eung da phdng tau Selene, mdt loai tau quy dao Mat trang, ed camera quay phim Mat trang vcii do phan giai cao. Cdn tau vii tru Kuguya, do Nhat phdng len Mat trang nam 2007, cd may phan tich quang phd tia gamma va da tim thay d Mat trang cd nhieu uranium, hiia hen cd the eung cap ddi dao cho qua dat. Ngoai ra, cdn cd tau vii tru ciia My Deep Impact phdng tir 2005, cd nhiem via nghien cuu ben trong sao Chdi va nhirng va cham do sao Chdi gay ra, ed trang bj may phan tich phd rat nhay de tim ra nudc, hcri nudc trong sao Chdi. Deep Impact eiing dugc diing de nghien cim hcri nudc d Mat trang, nhan lite bay gan Trai dat va Mat trang, ciing nhu khi lam them nhiem vu ed ten ggi la EPOXl.
4. VAN DE N U d c TREN MATTRANG Mat trang lii vc tinh ciia Trai dat, theo thuyet Vu va cham lein thi cac chat cau tao nen Mat triing cimg lii cac chat cau tao nen Trai dat bj tung toe len do mot vat Icin va cham rdi bdi tti lai. Vii va cham lein xay ra khi Trai dat chira hoan toan thanh hinh vao khoang bdn ti rudi niim ._ trirdc diiy. Sau dd cd 3,9 ty nam trudc day theo nhung khao sat ky luting thi Trai dat ludn bj ' '. nhirng tran ban pha cua thien thach va sao chdi. Chinh thien thach va dac biet la sao chdi dem lai cho Trai dat rat nhieu nudc ciing nhu cac thanh phan ciia nude lii hydrd va oxy. Ba phan tu be mat ciia Trai dat la nude, tdn tai cho den nay. Mat trang eung hinh thanh khi Trai dat edn non tre, dien tich Mat trang ciing kha Icin. chac chiin lii Mat triing ciing bj thien thach vii sao chdi ban pha manh vii nhiing tran ban pha nay ciing phai dem lai cho Mat triing rat nhieu nudc. Vay thi nudc tren Mat triing di dau?
Co rat nhieu ly do cho thiiy nudc tren Miit trang bj hao htit, can kiet di giin het chukhdng the con lai nhieu nhu d Trai diit. Trucic het, dd la vi luc hiip dan ci Mat triing rat nhd so vdi luc hap dan ciTrai dat, khi quyen ci Mat triing rat mdng. hau nlur khdng cd. .\nh sang
thang 10 20i Khoa hoc & T6 au6c 1 5
I KHOA HQC
Mat trcri chieu thing den be mat Mat trang, khdng gi ngan can lai. Do dd nhiet do d Mat trang ndng nhat Itic cd Mat trdi den 123''C, liic ban dem Mat trcri khdng chieu nira, nhiet do cd the giam den -133''C.
Trong nhung dieu kien nhu vay, nudc thu thap dugc bao nhieu se bay hoi len, tan di xa vao khdng trung rdi mat hiit. Mat trang khdng giir nudc lai dugc.
Mat trang rat khd cdn la de hieu. Nhung dieu chua tra ldi dugc la nudc da bay hcri phan tan di ca hay cdn lai it nhieu.
Cac chuyen bay dau tien ctia chucmg trinh Apollo chii yeu khao sat Mat trang bang rada nen chira tra ldi dugc la tren Mat trang cd cdn nudc hay khdng.
Nhung nhung chuyen bay nay cung cap nhieu dii lieu chiing td Mat trang hinh thanh la do va cham.
Ma da la hinh thanh do va cham thi cd kha nang la nudc it nhieu van con. Nam 1994tauviitruClementine lam nhiem vu ve chi tiet be mat Mat trang, Clementine da lam thii mot thi nghiem la chieu sdng radio vao mdt hd sau d gan nam cue ciia Mat trang. Sdng radio phan xa dugc hucing cho di thang ve Trai dat de ang ten tren Trai dat thu va phan tich. Ket qua phan tich la sdng radio ed ve nhu la phan xa bdi be mat nudc da. Neu diing vay thi dieu nay rat cd y nghTa: trudc day tren Mat trang cd nhieu nudc, rdi hau het nudc da bay hcri va thoat khdi Mat triing nhung van cdn cd nudc d nai sau, bj ddng bang do anh mat trcri bj khuat khdng chieu sang dugc; nudc van cdn ducii dang nudc da.
Tuy nhien, each dung sdng radio phan xa de tim nudc da ciia Clementine chua thuc chac chan. Cac nha khoa hgc lai dimg phucmg phap chieu rada vao be mat ciia mieng hd sau do', nhung dung he thdng thu sdng rada cao cap dat d Puerto Rico de thu. Ket qua la khdng tim thay cd nudc da. Vay cd phai la ket qua ma tau Clementine tim ra trudc day la sai hay khdng?
Nam 1998 Nasa da phdng Lunar Prospector de kiem tra bang each chieu tia nertron xudng be mat hd d nam cue ctia Mat trang. Ket qua lai cho thay d ddy cd rat nhieu hydrd. Nhung dd cd phai la hydrd (H) ciia nudc (H:0) hay khdng thi chua ai k8t luan dugc chac chan. Biet dau dd la mdt khoang chdt giau hydrd chii khdng phai la nudc da. De tim hieu dd cd phai la nudc hay khdng, tham chi ngucri ta da hy sinh ca con uiu Lunar Prospector. Khi nhiem vu da hoan thanh, ngucri ta cho ca eon tau Lunar Prospector dam
sdm vao Mat trang, hy vgng la nd se cay xdi mdt dien tich nhd ctia Mat trang, lam tung len vai manh nhd cd chiia nudc de phan tich bdng cac phuang tien dat dTrai ddt. Con tau Lunar Prospector da dam xudng Mat trang, nhung nhiing nha khoa hgc tren mat dat chua tim dugc bdng chiing tnrc tiep nao chirng to Mat trang cd nudc ca.
Vi vay, trong mdy nam gan day cac nha khoa hoc tap trung cac phuang tien de true tiep kiem tra la tren Mat trang cd nudc that hay khdng. Viia qua da cd cdng bd ba phan tich rieng re diing du lieu tii ve tinh Chandrayaan -1 ciia An Do va hai tau vu tni ctia My la Deep Impact va Cassini da tim thay bang chiing la cd nudc tren Mat trang. Ket qua that chi tiet thi edn phai dcyi cdng bd chinh thiic tren td Science ngay 24 thang 9 nam 2009, nhung budc dau cho biet nudc tim thay dugc dd khdng phai la nudc d dai duong, hd, ao tham chi la viing nhd. Dd chi la nhirng phan tli nudc va hydroxyl (gdm hydrd va oxy) tucmg tac vcii cac phan tu bui va da d Idp tren ciing ciia be mat Mat trang. Va de dimg qua hy vgng cd the khai thae nhieu nudc tren Mat trang, trong cudc hgp bao ciia Nasa cdng bd van de nay nha khoa hgc Roi Green ndi: "Ngay ca nhung sa mac khd cdn nhat tren Trai dat cung cd nhieu nudc ban d hai cue ciia Mat trang".
Hien nay dang cdn nhieu tau vu tnr tham dd tim hieu van de nudc tren Mat trang, cd tau thang 10 nam 2009 nay se den va cho biet ket qua.
Trong thdi chien tranh lanh, hai cudng quoc My va Lien Xd rdt chti y den Mat trang vi ly do quan su. Nhung sau nay thi rat nhieu nudc chii y den Mat trang vi Trai dat da la ddt chat ngucri ddng phai dan dan tim each thoat ra khdi Trai dat tim khoang san, nang lucyng, tim nai trung chuyen de di nhirng hanh tinh khac phong phii ma cdn hoang da. Nudc rdt can cho susdng, dau la sdng lau dai hay song tam bg. Mien la cd mdt it nudc d Mat trang, con ngudi se cd each lam cho nhieu nudc ban, tir nudc lam ra nhien lieu (hydrd) de tiep te cho nhirng chuyen di xa, vi di tir mat dat thi phai vugt lire hdp dan lein, lap khi quyen day, rat tdn kem.
Nhu vay, ndi den Mat trang nhieu ngudi nghT den hinh anh chj Hdng dep de nhdt la vao djp Trung thu.
Nhung ciing da bdt dau phd bien cum tir "thugc dja tren Mat trang" (colony on the Moon) cho thay dang cd mdt cudc chay dua ve ky thuat de chiem dung Mat trang. •
Khoa hoc & Td qu6c thang 10 2009