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.
At its closest (perihelion), Mars is 128 million miles (206 million km) distant. On average, the distance to Mars from the sun is 142 million miles (229 million km), according to NASA. Mars revolves around the sun in 687 Earth days, which represents a Martian year. Measuring the distance