The phrase "triumph of interplanetary exploration" can be replaced by several synonyms to enhance the impact of the statement. For instance, you can use "victory of space exploration" to convey the message of conquering the unknown frontiers of our solar system. Additionally, "achievement of intergalactic exploration" highlights the remarkable accomplishments of scientists and space agencies that have pushed the boundaries of space travel. The phrase "success of interstellar exploration" portrays a sense of triumph in the quest for other habitable planets. In conclusion, the synonyms for the phrase "triumph of interplanetary exploration" provide alternative ways to express the awe-inspiring feats of space exploration and the pursuit of knowledge beyond our planet.