Read enough about space exploration and you detect a common theme: the universe contains all sorts of wonders, but we don't have enough money to properly explore them.

We've discovered liquid oceans on several different moons in our solar system, but cuts to NASA's planetary science budget (the money it can spend on exploring other planets and moons) mean we won't be sending probes to them for at least a decade. Congress has directed NASA to develop the biggest rocket ever, but it's unclear whether there will be money to actually use it once it's finished.

It doesn't have to be this way. The price tags for NASA and its various programs might sound big, but put into context they're fairly modest. Here, inspired by the excellent blog Things That Cost More Than Space, are some of the things we routinely spend much more public money on:

1) The F-35 fighter will cost more than sending humans to Mars

Development of the F-35 Joint Strike Fighter has spiraled out of control, escalating to a total cost of about $1.5 trillion over the course of 50 years, or $29 billion per year.

Generous estimates for a human Mars mission peg its total cost at around $100 billion over 20 years, or $5 billion per year. (Thanks to the Planetary Society's Casey Dreier for this comparison.)

2) The Postal Service costs more than exploring other planets

The US Postal Service lost money last year, costing the federal government $5.5 billion.

NASA's budget for planetary science — all its programs to explore the moons and planets of our solar system — was $1.35 billion.

3) Improper Medicare payments cost more than NASA's whole budget

In 2013, Medicare made $45.7 billion in what the Government Accountability Office calls "improper payments." These are a mix of payments sent to the wrong people, accidental overpayments, and, to a large extent, outright fraud.

NASA's entire 2013 budget was just $16.8 billion.

4) NFL stadiums cost taxpayers more than exploring Jupiter's moon

Since 2000, US taxpayers have spent an estimated $3.9 billion on football stadiums for profitable, privately held NFL teams.

Meanwhile, after years of being told that uncrewed missions to Jupiter's moon Europa (which is believed to have a water ocean underneath its icy surface) were too expensive, NASA has gotten approval for a streamlined, cheaper probe that will orbit Jupiter instead of Europa itself. That probe will cost taxpayers about $2 billion.

5) Destroyed weapons cost more than the Curiosity Mars rover

As it wound down the war in Afghanistan, the US military destroyed or abandoned more than $7 billion worth of weapons and other military equipment.

NASA's Curiosity rover cost $2.5 billion to develop, launch, and send to Mars.

6) Making pennies and nickels costs more than operating a threatened Mars rover

As Things That Cost More Than Space points out, because it costs more for the US Mint to make pennies and nickels than they're actually worth, the government lost $105 million on the coins last year.

Meanwhile, to cut costs, NASA has repeatedly considered shutting down operation of the Opportunity rover, which landed on Mars in 2004 and is still collecting data, surviving 40 times longer than its original projected lifespan. It costs $14 million a year to operate.

7) Payments to dead federal workers cost more than NASA's mission to Pluto

In 2013, the government's Office of Personnel Management accidentally sent $84.7 million in payments to retired federal workers who'd already died — slightly less than in the previous few years.

By contrast, the New Horizons spacecraft, launched in 2006 and due to reach Pluto this summer, cost a total of $700 million, or $77.8 million per year.