Abstract
More than 40 years after the first successful landing on Mars, in situ exploration of its surface continues to be a huge scientific and technological challenge. This primarily refers to Martian southern highlands, extending over a large part of its southern hemisphere, where no successful landing has been achieved so far. On the other hand, in the northern lowlands, which cover almost entire northern hemisphere, 7 successful landings have been completed. This difference is a consequence of the specific topography of the Martian surface due to the so-called global or hemispherical dichotomy of Mars, which represents a unique feature in the Solar system. Due to the difference in elevations of the surface, a spacecraft trying land on the southern highlands have a thinner atmosphere layer which can be used for dissipation of kinetic energy. Since the spacecraft from an interplanetary trajectory enter the atmosphere with hyperbolic velocities, their kinetic energy is extremely large and the ability to reduce it through interaction with the atmosphere is crucial for safe landing, especially at sites with high elevation. It is estimated that the southern highlands are billions of years older than the northern lowlands, which were exposed to strong volcanic activity in the relatively recent past. This huge difference in age is a motivation for exploration of the entire surface of Mars in order to understand its complex geological evolution. In addition, a large number of open basins, which were discovered on the southern lowlands, indicate that these regions in the past could have been covered with liquid water, which is one of the most important reasons for exploring these locations. The analysis of the seasonal and daily variations of the Martian atmosphere confirms that, it is possible to land on these high locations by using current technology, with the necessity of optimization of the conditions under which spacecraft enter the atmosphere, in order to maximize the benefits from these specificities of Mars.
Highlights
Uočljivo je da se visina otvaranja padobrana za sletanja na istu lokaciju i pri istim početnim uslovima, menja za nekoliko kilometara tokom Marsove godine, što je više od srednje razlike u elevacijama severne i južne hemisfere
Na slici 14 su prikazane ove lokacije na delu južne hemisfere Marsa, za početnu brzinu, ugao nagiba putanje i minimalno vreme spuštanja od 57 sekundi, kao što je bilo za misiju Mars Exploration Rover (MER)-B (Opportunity)
This huge difference in age is a motivation for exploration of the entire surface of Mars in order to understand its complex geological evolution
Summary
Razlozi zbog kojih sletanje na Mars i nakon 16 pokušaja predstavlja toliko veliki tehnološki izazov su pre svega posledica činjenice da je Marsova atmosfera dovoljno gusta i debela da uzrokuje značajno zagrevanje letelice koja u nju ulazi hiperboličkom brzinom (brzina na hiperboličkoj orbiti oko nebeskog tela), a sa druge strane nije dovoljno gusta i debela da letelicu uspori dovoljno da se izvrši bezbedno sletanje. Rezultat ove činjenice je da letelice koje ulaze u atmosferu Marsa počinju značajnije da usporavaju, usled otpora atmosfere, na mnogo manjim visinama nego što je to slučaj prilikom sletanja na Zemlju. Zbog ovoga je visina atmosferskog sloja kroz koji letelica prolazi od ključnog značaja za uspešno sletanje i glavni razlog zbog kojeg je svih sedam uspešnih sletanja do sada izvršeno u niskim oblastima na severnoj hemisferi i u ekvatorskoj oblasti. Ovo predstavlja naizgled apsurdnu situaciju, jer se četiri decenije nakon sletanja Vikinga i još pet uspešnih sletanja pomoću letelica koje su bile bazirane na istoj tehnologiji, na Mars šalje letelica mase 600 kg koja nema gotovo nikakve naučne ciljeve, već joj je jedini cilj da ispita i demonstrira već postojeće tehnologije. Kada bi na površini Marsa postojala voda u odgovarajućoj količini, ona bi zauzela oblik upravo ove površine
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