Sourced

• Since 'tis certain that Earth and Jupiter have their Water and Clouds, there is no reason why the other Planets should be without them. I can't say that they are exactly of the same nature with our Water; but that they should be liquid their use requires, as their beauty does that they be clear. This Water of ours, in Jupiter or Saturn, would be frozen up instantly by reason of the vast distance of the Sun. Every Planet therefore must have its own Waters of such a temper not liable to Frost.
• What a wonderful and amazing Scheme have we here of the magnificent Vastness of the Universe! So many Suns, so many Earths, and every one of them stock’d with so many Herbs, Trees and Animals, and adorn’d with so many Seas and Mountains! And how must our wonder and admiration be encreased when we consider the prodigious distance and multitude of the Stars?

Disputed

• The world is my country, to promote science is my religion.
  • The earliest citation of this remark yet found is in The Making of Modern Europe, 1648-1780 (1985) by Geoffrey Treasure, p. 474, where it is declared that this was Huygens' "motto" — but this seems very similar to the much more famous and long attested declaration of Thomas Paine in Rights of Man (1791): "My country is the world, and my religion is to do good." which has long been paraphrased "The world is my country, and to do good is my religion."
  • The world is my country, science my religion. from Cosmos: A Personal Voyage - Episode 6 - Huygens