Many names were slightly changed, but it wasn't quite of a problem.
Changes:
Mars >> Marte
Dr. Kawashimo >> Dr. Cawa
Dr. Yamanoue >> Dr. Yama
Miri >> Milly
Melchi >> Melki
In Brazil Jetter Mars came as "O Menino Biônico" (The Bionic Boy) despite being actually a robot.
The reason for that missleading name is the fact they wanted to call the attention of the children who had been familiar with movies like the "Bionic Woman" for example.
Since Brazil had good relations with Japan ever since 1895, the dub did their best to not adapt the story-line or hide it's japanese origins.
Although Brazil got involved with the WW2 and at the side of USA, the relationship with Japan was still friendly during the time which the anime aired.
With many japanese living here during that time, we don't had any misconception with the original names of the series.
Well, most names ended becoming puns in old american dubs (mostly due the misconception of the public about japanese works and language), but wasn't the case in Brazil.
Misconception of cultures is a horrible thing and I cannot stand it when it comes to adapted animes.
So, most of what the japanese got was basically unchanged in Jetter Mars and it even the introduction and ending was keept.
There was no intention of hidding the japanese origins in the brazilian dubs back then...
Although, some voices doesn't sounded quite well in the brazilian version, like Jetter Mars who was voiced by Carlos Marques (that's how he looks nowadays, not how he was when the anime aired of course.):
Carlos Marques used the same voice which he did in Mighty Mouse (Super Mouse in the dub) which made Mars (Marte in the dub) sound much older than his looks.
If you thought that Astro Boy in 2003 sounded older than he looks, then you can't imagine how older Marte sounded.
While Orlando Drummond did Dr. Cawa:
Orlando Drummond is pretty know for voicing characters like Scooby-Do, Popeye and ALF (from the TV series of same name).
Despite dubbing Dr. Cawa in Jetter Mars, he was not choosen to voice Dr. O'shay in the brazilian dub, but instead he voiced Duke Red in the final episodes of 2003 series.
By curiosity, there is a rumor that some company who sold sweet popcorn used Jetter Mars image in the package.
It does sounds hilarious and awful at same time since these popcorn were not licensed by Toei Animation.
It was said, the popcorn was still sold till 90s.
Unfortunatelly, the brazilian dub of the series was lost and no DVD release was officially made.
Even the small fragment of episode 4 is no longer available in youtube.
There was a lot of dedication at dubbing back then in Brazil that none of the brazilians can see in good eyes the american dub in animes.
But due licensing issues and the fact translating groups feels the english dub easier to take a base we end up getting the same cuts and name changes.
It often don't ensure the quality of the episodes and in special if the DVDs don't give the original japanese voices.
If Jetter Mars got the dubbed episodes restored and with the original japanese dub, then it would marvelous.
A example of such quality was seem in Dengeki Sentai Changeman which they gave the original dub with high quality and as well the original japanese episodes subbed.
