The Temple of Mars Ultor, Mars the Avenger, was the centerpiece of The Forum of Caesar Augustus. Its podium (the platform on which it was built) along with four re-erected marble columns and architrave as well as the re-emplaced altar are still visible from Via Alessandrina, the pedestrian road that angles across the Fori Imperiali excavations in Rome. For a better view of the architectural details, walk around behind on Via Tor de Conti and peer through the large conveniently-placed arch that pierces the high pepperino-stone wall that served as a firebreak separating the extremely flammable ancient Suburra slum from the more highly valued buildings in the Forums. Augustus built the temple to celebrate the defeat and death of the conspirators who assassinated Julius Caesar, the uncle and adoptive father of Augustus. Mars, the God of War, had once again intervened and assured victory for Roman right and justice.
The Greeks had had a realistic view of war and of the God with whom they personified war. Ares was a chaotic and indiscriminate villain. He was not at all interested in who won the wars among the Greek city-states, and, rather than intervene to bring victory to either side, his only goal was to prolong conflict to increase the body count and ensure maximum bloodshed. Ares, to the Greeks, was literally bloodthirsty, and their pictorial and literary imagery emphasized that aspect of the god. Ares was hated and feared by all, but he was especially hated by the women -- Ares took off their fathers, husbands, sons, and the worst thing was that he could be depended on to repeatedly seduce their men into thinking that war, somehow, was a good way to resolve disputes. There never was any doubt among the Greeks -- even the men -- that Ares and the human activity that he personified were essentially horrible.
The Romans identified Mars with Ares, but their Mars was different. He was, after all, the progenitor of Romulus and Remus, having, one night, visited their mom, Rhea Sylvia, in her celibate's cell in the Vestal nunnery where her vile Uncle Amulius had immured here to prevent heirs in his brother's line. Thus Mars, like Venus, the mother of Aeneas, was a true parent of all Romans. This was especially true of the Julian gens (clan), from which both Julius Caesar and Octavian (Caesar Augustus) had sprung: Julus, the son of Aeneas and grandson of Venus, was the founder of the Alba Longa dynasty, and it was there that the whole Rhea Sylvia/Mars drama had been played out. It was only to be expected that Mars, the mythical father of Rome, would take sides and help in his children's conquests, and, whenever necessary, in their vengeance. So unlike Ares, who wanted everyone's blood, Mars particularly sought foreign blood. Roman blood, shed in "good wars", went to him also, but only to the extent that it was needed to ensure a Roman victory. And treasonous fellows, like Brutus and Cassius, who a had killed Julius Caesar, and like Cataline and, later, Marc Antony, who conspired with foreigners, had alienated themselves -- made themselves "foreign" -- by their treasonous actions and they were therefore deserving of vengeance.
So, to the Romans, Mars was a dependable "good guy", and war was always and uniformly justified for conquest or revenge. In the Roman view, you never had to worry that Mars would betray you at the last minute just to keep the battle going and the blood flowing -- unless, of course you crossed a line and did something treasonous or, possibly, unless you hadn't absorbed the military principles of the cult of Mars, that is, if you were just an inept general. Victories came from Mars and defeats came from human treason or ineptitude. This was a comforting way of looking at the War God and also a pretty good rationalization for a continuous Roman policy of war against weaker neighbors. And by the time Rome started to lose wars, Mars, along with the other pagan Roman Gods, was already in decline. He still wasn't to be blamed: rather it was the falling away from his worship that caused the problems. All a neatly tied up pro-Martian package, but by that time it didn't matter -- Rome and all of its gods were already passe.
Fast-forward a millennium and a half, and we moderns see that Mars is only a planet and no longer a God. At first the modern Mars was all Pietro Secchi's and Giovanni Schiaparelli's "canali". Foreigners mistranslated "canali" as "canals" when it really meant "channels", and thus added a misleading connotation of artificial construction, presumably by Martians, that had never been intended by the two Italian astronomers. Percival Lowell, a great American astronomer, mapped the "canals" and thought he saw cities at their intersections. Soon Mars was crawling with folks like Thuvia and other Burroughs Barsoom characters -- still a good read at http://www-2.cs.cmu.edu/People/rgs/. It's too bad that late 20th century science brought it all back to reality -- of a sort. Or rather of various sorts: the scientists still can't decide which of their theories truly describe Mars, even after orbiters, probes, Mars-landers, mini-rovers, and unintended crash landings on the surface.
But they are getting closer, both in their actual imagery of the planet and in their interpretations of what they see. The latest pictures, the most detailed ever, are provided by the THEMIS package on the NASA "Mars Odyssey 2001" orbiter. A new Internet site came on line on march 27, 2002, on which a new image is posted daily, drawn from the many daily pictures taken by the THEMIS infrared imaging system. Eventually thousands of THEMIS images will be electronically stitched together into a new Martian surface map. For now, every day you can see a new patch, which will eventually be part of the surface quilt, at http://themis.asu.edu/latest.html.
One reasonably up-to-date version of "What we know about Mars" -- the planet, not the god -- is at http://www.spacetoday.org/SolSys/Mars/MarsWater.html, but be aware that "knowledge" changes quickly: in the last week of March, 2002, another theory was reinforced, which posits debris flows levitated by evaporating solid and liquid carbon-dioxide as the true cause of channels that also look like they may have been cut by water erosion (at http://unisci.com/stories/20021/0327022.htm). Theories about the formation of Martian surface features are like early April weather in Rome -- you wait a minute for it to change (http://www.cnn.com/WEATHER/eu/Italy/RomaRMLIRF.html).
P.S. 1: Planet Mars will participate in two extremely rare multi-planet alignments late April and early May of 2002. There will be another in 2040, but that one will be much closer to the horizon and therefore not very visible to the naked eye, so don't miss your 2002 viewing opportunities. Details are at http://www.space.com/scienceastronomy/solarsystem/planets_align_020402-1.html.
P.S. 2: How do I find all this good astronomy info? Actually, it finds me, because I subscribe to a free Internet science info service. If you're interested in keeping up with scientific developments as reported in reputable world scientific publications (i.e., not "New Wave", nor UFO, nor quasi-religious pubs), subscribe at http://newsletter.scicentral.com/cgi-bin/register.cgi.
Go to http://www.mmdtkw.org/Veneto2002.html for other articles.