No you do not have to appear in court for certain offenses. In your case, you were going 39 over the posted speed limit. In MD, most traffic fines are fixed rates, with a "Must Appear" flag only applicable for the most serious offenses. And if you had committed one of those, the ticket (The "MARYLAND UNIFORM COMPLAINT AND CITATION") would have had the box checked next to "YOU MUST APPEAR FOR TRIAL WHEN NOTIFIED BY THE COURT."
Exceeding the limit by 39 mph carries a fine of $290 and 5 points against your license. You can:
1. Pay the fine by mailing it in, which is in effect also pleading guilty and avoiding a court date.
2. Plead "guilty with explanation." Send the form in with the box indicating you want to do this, then appear in court to explain to the judge. This is recommended as the judge can choose to lower your fine or not give as many points.
3. Do nothing and wait for a trial date to be set. Do this if you wish to contest the ticket and plead not guilty.