The sea wasp box jellyfish is perhaps the most deadly variety. This translucent sea-dweller may not look all that menacing, but it is the most venomous animal on planet Earth. Box jellyfish are deadly to many different animals, not the least of all, us. If you get stung by one of these animals, you are very likely to die.
Earth and Mars Conjunction: On the opposite end of the scale, Mars and Earth can be 401 million km apart (249 million miles) when they are in opposition and both are at aphelion. The average distance between the two is 225 million km. When Mars and Earth are at their closest, you have your launch window.
The last Mars opposition occurred on May 22, 2016 at a distance of about 76 million km. The next Mars opposition occurs on July 27, 2018 at a distance of about 58 million km. The average time between the successive oppositions of Mars, its synodic period, is 780 days; but the number of days between the dates of successive oppositions can range from 764 to 812.