Free Astronomy Magazine November-December 2024 ARABIC VERSION

escape, they can understand the processes that determined the es- cape rates over the last four billion years and thereby extrapolate back in time. Although most of the study’s data comesfromtheMAVENspacecraft, MAVEN is not sensitive enough to see the deuterium emission at all timesoftheMartianyear.Unlikethe Earth,MarsswingsfarfromtheSun initsellipticalorbitduringthelong Martian winter, and the deuterium emissionsbecomefaint.Clarkeand histeamneededtheHubbledatato “fillintheblanks”andcompletean annualcycleforthreeMartianyears (each of which is 687 Earth days). Hubble also provided additional data going back to 1991 – prior to MAVEN’s arrival at Mars in 2014. The combination of data between thesemissionsprovidedthefirstho- listicviewofhydrogenatomsescap- ing Mars into space. “In recent years scientists have foundthatMarshasanannualcycle that is much more dynamic than peopleexpected10or15yearsago,” explainedClarke. “Thewholeat- mosphereisveryturbulent,heating up and cooling down on short timescales,evendowntohours.The atmosphere expands and contracts asthebrightnessoftheSunatMars variesby40percentoverthecourse of a Martian year.” Theteamdiscoveredthattheescape rates of hydrogen and deuterium changerapidlywhenMarsisclose to the Sun. In the classical picture that scientists previously had, these atoms were thought to slowly dif- fuse upward through the atmos- phere to a height where they could escape. But that picture no longer accu- ratelyreflectsthewholestory,be- cause now scientists know that atmosphericconditionschangevery quickly. When Mars is close to the Sun, the water molecules, which are thesourceofthehydrogenanddeu- terium,risethroughtheatmosphere veryrapidlyreleasingatomsathigh altitudes. The second finding is that the changesinhydrogenanddeuterium aresorapidthattheatomicescape needsaddedenergytoexplainthem. Atthetemperatureoftheupperat- mosphere only a small fraction of theatomshaveenoughspeedtoes- cape the gravity of Mars. Faster (super-thermal) atoms are producedwhensomethinggivesthe atom a kick of extra energy. Theseeventsincludecollisionsfrom solar wind protons entering the at- mosphere or sunlight that drives chemicalreactionsintheupperat- mosphere. Studying the history of water on Marsisfundamentalnotonlytoun- derstanding planets in our own so- lar system but also the evolutionof Earth-size planets around other stars.Astronomersarefindingmore and more of these planets, but they’re difficult to study in detail. Mars, Earth and Venus all sit in or near our solar system’s habitable zone,theregionaroundastarwhere liquid water could pool on a rocky planet; yet all three planets have dramatically different present-day conditions. Along with its sister planets, Mars can help scientists graspthenatureoffar-flungworlds acrossourgalaxy.      ﻧﻮﻓﻤﺒﺮ - ﺩﻳﺴﻤﺒﺮ 2 0 2 4 ﻋﲆ اﻟﺮﻏﻢ ﻣﻦ أن ﻣﻌﻈﻢ ﺑﻴﺎﻧـﺎت اﻟ ﺪراﺳـﺔ ﺗﺄﺗﻲ ﻣﻦ ﻣﺮﻛﺒﺔ اﻟﻔﻀﺎء ﻣﺎﻓﻦ إﻻ أن ﻣﻬﻤﺔ ا ﺴﺒﺎر ﻣﺎﻓﻦ ﻟﻴﺴﺖ ﺣﺴﺎﺳـﺔ ﺑﻤـﺎ ﻳﻜﻔـﻲ ﻟﺮؤﻳﺔ اﻧﺒﻌﺎﺛﺎت اﻟﺪﻳﻮﺗ ﻳﻮم ﰲ ﺟﻤﻴﻊ أوﻗﺎت اﻟﺴﻨﺔ ا ﺮﻳﺨﻴﺔ وﻋﲆ ﻋﻜﺲ اﻷرض ﻳﺘﺄرﺟﺢ ا ــﺮﻳﺦ ﺑﻌﻴــﺪ اً ﻋــﻦ اﻟﺸــﻤ ﺲ ﰲ ﻣــﺪاره اﻹﻫﻠﻴ ﻠﺠﻲ أﺛﻨﺎء اﻟﺸـﺘﺎء ا ﺮﻳﺨـﻲ اﻟﻄﻮﻳـﻞ وﺗﺼﺒﺢ اﻧﺒﻌﺎﺛﺎت اﻟﺪﻳﻮﺗ ﻳﻮم ﺿﻌﻴﻔﺔ . اﺣﺘﺎج ﻛﻼرك وﻓﺮﻳﻘﻪ إﱃ ﺑﻴﺎﻧﺎت ﺗﻠﺴـﻜﻮب " ﻫﺎﺑﻞ ـﻞء اﻟﻔﺮاﻏـﺎت " واﺳـﺘﻜﻤﺎل دورة ﺳﻨﻮﻳﺔ ﺪة ﺛﻼث ﺳﻨﻮات ﻣﺮﻳﺨﻴﺔ ) ﻛﻞ ﻣﻨﻬﺎ 686 ﺎً ﻳﻮﻣ أرﺿﻴ (. ﺎً ﻛﻤﺎ ﻗﺪم ﺗﻠﺴﻜﻮب ﻫﺎﺑﻞ ﺑﻴﺎﻧـﺎت إﺿـﺎﻓﻴﺔ ﺗﻌﻮد إ ﱃ ﻋﺎم 1991 ﻗﺒﻞ وﺻـﻮل ﻣـﺎﻓﻦ إﱃ ا ﺮﻳﺦ ﰲ ﻋﺎم 2014 . ﻟﻘﺪ وﻓﺮ اﻟﺠﻤـﻊ ﺑـ اﻟﺒﻴﺎﻧـﺎت ﻣـﻦ ﻫـﺬه اﻟﺒﻌﺜﺎت اﻟﻌﻠﻤﻴﺔ أول رؤﻳـﺔ ﺷـﺎﻣﻠﺔ ﻟـﺬرات اﻟﻬﻴﺪروﺟ اﻟﺘﻲ ﺗﻬﺮب ﻣﻦ ﻛﻮﻛﺐ ا ﺮﻳﺦ إﱃ اﻟﻔﻀﺎء . أوﺿﺢ ﻛﻼرك : " ﰲ اﻟﺴﻨﻮات اﻷﺧـ ة وﺟـﺪ اﻟﻌﻠﻤ ـﺎء أن دورة ا ـﺮﻳﺦ اﻟﺴ ـﻨﻮﻳﺔ أﻛﺜ ـﺮ دﻳﻨﺎﻣﻴﻜﻴﺔ ﻣﻤﺎ ﺗﻮﻗﻊ ﻗﺒﻞ 10 أو 15 ."ﻋﺎﻣﺎً " إن اﻟﻐــﻼف اﻟﺠــﻮي ﺑﺄﻛﻤﻠ ـﻪ ﻣﻀــﻄﺮب ﻟﻠﻐﺎﻳﺔ، ﺣﻴﺚ ﻳ ﺴـﺨﻦ وﻳـﱪد ﻋـﲆ ﻓـﱰات زﻣﻨﻴﺔ ﻗﺼ ة ﺣﺘﻰ ﺳﺎﻋﺎت وﻳﺘﻤﺪد اﻟﻐﻼف اﻟﺠﻮي وﻳﻨﻜﻤﺶ ﻣﻊ ﺗﻐ ﺳﻄﻮع اﻟﺸﻤﺲ ﻋﲆ ا ﺮﻳﺦ ﺑﻨﺴﺒﺔ 40 % وذﻟﻚ ﻋﲆ ﻣﺪار ﻋﺎم اﻟﻐﻼف اﻟﺠﻮي وﻳﻨﻜﻤﺶ ﻣﻊ ﺗﻐ ﺳـﻄﻮع اﻟﺸﻤﺲ ﻋﲆ ا ﺮﻳﺦ ﺑﻨﺴﺒﺔ 40 % وذﻟﻚ ﻋـﲆ ﻣﺪار ﻋﺎم ﻣﺮﻳﺨﻲ ". اﻛﺘﺸﻒ ا ﻟﻔﺮﻳﻖ اﻟﻌﻠﻤﻲ أن ﻣﻌﺪﻻت ﻫﺮوب اﻟﻬﻴﺪروﺟ واﻟﺪﻳﻮﺗ ﻳﻮم ﺗﺘﻐـ ﺑـ ـ ﴪﻋﺔ ﻋﻨ ﺪﻣﺎ ﻳﻜﻮن ا ﺮﻳﺦ ﻗﺮﻳﺒﺎً ﻣﻦ اﻟﺸـﻤﺲ وﰲ اﻟﺼﻮرة اﻟﻜﻼﺳـﻴﻜﻴﺔ اﻟ ﺘـﻲ ﻛـﺎن اﻟﻌﻠﻤـﺎء ﻳﻤﺘﻠﻜﻮﻧﻬﺎ ﺳﺎﺑﻘﺎً ﻛﺎن ﻳُﻌﺘﻘﺪ أن ﻫﺬه اﻟﺬرات ﺗﻨﺘﴩ ﺑﺒﻂء إﱃ أﻋﲆ ﻋﱪ اﻟﻐﻼف اﻟﺠ ﻮي إﱃ ارﺗﻔﺎع ﺣﻴﺚ ﻳﻤﻜﻨﻬﺎ اﻟﻬﺮوب . ﻟﻜﻦ ﻫﺬه اﻟﺼﻮرة ﻟﻢ ﺗﻌـﺪ ﺗﻌﻜـﺲ اﻟﻘﺼـﺔ ﺑﺎﻟﻜﺎﻣﻞ ﺑﺪﻗﺔ ﻷن اﻟﻌﻠﻤﺎء ﻳﻌﺮﻓـﻮن اﻵن أن اﻟﻈﺮوف اﻟﺠﻮﻳﺔ ﺗﺘﻐ ﺑﴪﻋ ﺔ ﻛﺒ ة . ﻋﻨـﺪﻣﺎ ﻳﻜـﻮن ﻛﻮﻛـﺐ ا ـﺮﻳﺦ ﻗﺮﻳﺒــ ﺎً ﻣـﻦ اﻟﺸﻤﺲ ﺗﺮﺗﻔﻊ ﺟﺰﻳﺌـﺎت ا ـﺎء اﻟﺘـﻲ ﺗﻌـﺪ ﻣﺼـﺪر اﻟﻬﻴ ـﺪر وﺟ واﻟ ـﺪﻳﻮﺗ ﻳﻮم ﻋ ـﱪ اﻟﻐﻼف اﻟﺠﻮي ﺑ ـ ﴪﻋﺔ ﻛﺒ ة وﺗﻄﻠﻖ ذرات ﻋﲆ ارﺗﻔﺎﻋﺎت ﻋﺎﻟﻴﺔ . اﻟﻨﺘﻴﺠــﺔ اﻟﺜﺎﻧﻴــﺔ ﻫــﻲ أن اﻟﺘﻐــ ات ﰲ اﻟﻬﻴﺪروﺟ واﻟﺪﻳﻮﺗ ﻳﻮم ﴎﻳﻌـﺔ ﻟﻠﻐﺎﻳـﺔ ﺑﺤﻴـﺚ ﻳﺤﺘـﺎج ا ﺸـﻬﺪ اﻟـﺬري إﱃ ﻃﺎﻗـﺔ إﺿﺎﻓﻴﺔ ﻟﺘﻔﺴ ﻫﺎ . ﻋﻨﺪ درﺟﺔ ﺣﺮارة اﻟﻐـﻼف اﻟﺠـﻮي اﻟﻌﻠـﻮي ﻟﻠﻤﺮﻳﺦ ﻻ ﻳﻔﻠﺖ ﺳـﻮى ﺟـﺰء ﺻـﻐ ﻣـﻦ اﻟﺬر ات ﻣﻦ ﺟﺎذﺑﻴﺔ ا ﺮﻳﺦ ﺑ ـ . ﴪﻋﺔ ﻛﺎﻓﻴـﺔ أﴎع ) ﺣﺮارﻳﺔ ﻓﺎﺋﻘﺔ ( ﻋﻨﺪﻣﺎ ﻳﻌﻄـ ﻲ ﳾء ﻣـﺎ اﻟـﺬرة دﻓﻌـﺔ ﻣـﻦ اﻟﻄﺎﻗـﺔ اﻹﺿـﺎﻓﻴﺔ ـــــــ ﺗﻨﺘﺞ ذرات أﴎع ) ﺣﺮارﻳﺔ ﻓﺎﺋﻘـﺔ ( ﻋﻨـﺪﻣﺎ ﻳﻌﻄﻲ ﳾء ﻣ ﺎ اﻟـﺬرة دﻓﻌـﺔ ﻣـﻦ اﻟﻄﺎﻗـﺔ اﻹﺿﺎﻓﻴﺔ . ﺗﺘﻀﻤﻦ ﻫﺬه اﻷﺣﺪاث ﺗﺼﺎدﻣﺎت ﻣﻦ ﺑﺮوﺗﻮﻧﺎت اﻟﺮﻳﺎح اﻟﺸﻤﺴﻴﺔ اﻟﺘ ﻲ ﺗـﺪﺧﻞ اﻟﻐﻼف اﻟﺠﻮي أو ﺿﻮء اﻟﺸﻤﺲ اﻟﺬي ﻳﺤﺮك اﻟﺘﻔـﺎﻋﻼت اﻟﻜﻴﻤﻴﺎﺋﻴـﺔ ﰲ اﻟﻐـﻼف اﻟﺠـﻮي اﻟﻌﻠﻮي ﻟﻠﻤﺮﻳﺦ . إن دراﺳﺔ ﺗﺎرﻳﺦ ا ﺎء ﻋـﲆ ﻛﻮﻛـﺐ ا ـﺮﻳﺦ ﻳﻌﺘـﱪ أﻣـﺮ اً أﺳﺎﺳـﻴ ﺎً ﻟـﻴﺲ ﻓﻘـﻂ ﻟﻔﻬـﻢ اﻟﻜﻮاﻛﺐ ﰲ ﻧﻈﺎﻣﻨﺎ اﻟﺸـ ـ ﻤﴘ ﺑـﻞ وأﻳﻀـﺎ ﻟﺘﻄﻮر اﻟﻜﻮاﻛﺐ ﺑﺤﺠﻢ اﻟ ﻜﺮة اﻻﺿﻴﺔ ﺣـﻮل اﻟﻨﺠﻮم اﻷﺧﺮى . ﻳﻜﺘ ﺸﻒ ﻋﻠﻤﺎء اﻟﻔﻠ ﻚ ا ﺰﻳﺪ وا ﺰﻳﺪ ﻣﻦ ﻫﺬه اﻟﻜﻮاﻛــﺐ ﻟﻜ ـﻦ ﻣ ـﻦ اﻟﺼــﻌﺐ دراﺳ ـﺘﻬﺎ ﺑﺎﻟﺘﻔﺼﻴﻞ . ان اﻟ ﻜﻮاﻛﺐ ﻣﺜﻞ ا ـﺮﻳﺦ واﻷرض واﻟﺰﻫـﺮة ﺗﻮﺟﺪ ﰲ أو ﺑﺎﻟﻘﺮب ﻣﻦ ا ﻨﻄﻘـﺔ اﻟﺼـﺎﻟﺤﺔ ﻟﻠﺤﻴﺎة ﰲ ﻧﻈﺎﻣﻨﺎ اﻟﺸﻤﴘ وﻫـﻲ ا ﻨﻄﻘـﺔ ا ﺤﻴﻄﺔ ﺑﺎﻟﻨﺠﻢ ﺣﻴﺚ ﻳﻤﻜﻦ أن ﺗﻮﺟﺪ ا ﻴـﺎه ﰲ اﻟﺤﺎﻟـﺔ اﻟﺴـﺎﺋﻠﺔ وﻣـﻊ ذﻟـﻚ ﻓـﺈن ﻫـﺬة اﻟﻜﻮا ﻛﺐ اﻟﺜﻼﺛﺔ ﻟﻬﺎ ﻇﺮوف ﻣﺨﺘﻠﻔﺔ ﺗﻤﺎﻣـ ﺎً ﰲ اﻟﻮﻗﺖ اﻟﺤﺎﴐ . ﻳﻤﻜﻦ ﻟﻜﻮﻛﺐ ا ﺮﻳﺦ وا ﻟﻜﻮاﻛﺐ اﻟﺸﻘﻴﻘﺔ ﻟﻪ ﺗ أن ﺴﺎﻋﺪ ﻋﲆ ﻓﻬﻢ ﻃﺒﻴﻌﺔ اﻟﻌﻮاﻟﻢ اﻟﺒﻌﻴـﺪة ا ﻨﺘﴩة ﻋﱪ ﻣﺠﺮﺗﻨﺎ . ﻧﻘﻄـﺔ ـﺎرﻣـﻦ اﻟﺸـﻤﺲوا اﻻﺧﺘ ﺗﺴـﻤﻰ اﻷوج ﻓـﻲ ﻟــ 31 د ﺴـﻤ 2017 ــﺎﻟﻘﺮ و ﺗﺴﻤﻰ اﻟ ﻣﻦ أﻗﺮ ﻧﻘﻄﺔ ﻟﻬﺎ ﻣﻦ اﻟﺸﻤﺲواﻟ ـ ﺤﻀ ﺾﻫﺬﻩ ﻫﻲﺻﻮر ﺗﻠﺴ ﻮب ــــﺎﻟﻘﺮ ﻣــــﻦ أﻗﺼــــﻰ ﻧﻘﻄــــﺔ ﻟﻬــــﺎ ﻓــــﻲ ــــﺪة ﻟﻠﻤــــﺮ ﺦ ﻫﺎﺑــــﻞ ﻓــــﻮق اﻟ ﻨﻔﺴــــﺠ ﺔ اﻟ ﻌ 19 د ﺴـــﻤ 2016 . اﻟﻐـــﻼف اﻟـــ ـ ﺠﻮي ـــﻮن ﻳ أﻛـــ إﺷـــﺮاﻗ ﺎً واﻣﺘـــﺪاداً ﺸـــ ﻞ واﺿـــﺢ ﻋﻨـــﺪﻣﺎ ــﺎً ــﻮن اﻟﻤــﺮ ﺦ ﻗﺮ ﻳ ﻣــﻦ اﻟﺸــﻤﺲ . ﻈﻬــﺮﺿــﻮء اﻟﺸــﻤﺲ اﻟﻤــﻨﻌﻜﺲﻣــﻦ اﻟﻤــﺮ ﺦ ﻋﻨــﺪ ﻫﺬﻩ اﻷﻃﻮال اﻟﻤﻮﺟ ﺔ ﺗﺸﺘﺘﺎ ﺑﻮاﺳﻄﺔ ﺟﺰ ﺌﺎت اﻟﻐـﻼف اﻟـ ـ ﺠﻮيواﻟﻀـ ﺎب ﻓـﻲﺣـ ـــــﻮن اﻟﻘﻤــــــﻢ اﻟــــــ ﺗ ـ ــــــﺔ و ﻌــــــﺾ ﺠﻠ ﺪ ﺔ اﻟﻘﻄﺒ ﺗﻀـــــﺎرﺲ ــــــﺔ أ ﻀــــــﺎً اﻟﺴــــــﻄﺢ ﻣﺮ . أﻇﻬــــــﺮ ﺗﻠﺴــــ ﻮب ﻫﺎﺑــــﻞ و ﻣﺴــــ ﺎر ﻣــــﺎﻓﻦ أن اﻟﻈــــﺮوف اﻟــــ ـ ﺠﻮ ﺔ ﻟﻠﻤــــﺮ ﺦ ﺗﺘﻐــــ ﺴــــﺮﻋﺔ ﻛﺒــــ ة ﻌﻨﺪﻣ ﻓ اﻟﻤـﺮ ﺦ ﻣـﻦ اﻟﺸـﻤﺲ ﺗﺮ ﻔـﻊ ﺟﺰ ﺌـﺎت اﻟﻤـﺎء ﺴـﺮﻋﺔ ﻛﺒـ ة ﻋـ اﻟﻐـﻼف ﺎ ﻘ ـاﻟ ﺠﻮيﻓﺘﺘﻔ ﻚ وﺗﻄﻠﻖ اﻟﺬرات ﻋﻠﻰ ارﻔﺎﻋﺎت ﻋﺎﻟ ﺔ .