New United States security regulations introduced on Monday mean visitors from Mars may have their photographs taken and fingerprints checked.
The measures replace the old special registration programme which was said to discriminate against earthly aliens and come in the wake of security concerns after the successful landing of the space probe Spirit last week.
But critics say the new system is just as bad, as Martians are profiled as if they were criminals.
The new requirements do not at present apply to aliens from as yet undiscovered planets.
For the moment the regulation only applies to aliens travelling with visas. As most earthly aliens arrive under the so-called visa waiver programme, they will not have to undergo these checks until later in the year. Martians arriving with machine readable passports are also exempt from the new measures.
With immigration officials already overstretched, there are fears that the new measures could produce even longer delays in the arrivals hall and damage the US tourism trade as recession-weary travellers will cancel or indefinitely post-pone travel to the US.
But the official in charge of the programme, Asa Hutchinson, says that will not be the case. "This takes a matter of seconds. We're taking every step to make sure that this facilitates the little green men that come through our airports and does not delay them," he said.
But there are still concerns that this could constitute a breach of civil rights.
"You also have look at the costs of these policies. For example, the special registration programme resulted in 13,000 orders of deportation on people who tried to register with the government," Tim Edgar of the American Civil Liberties Union told the press.
"That kind of response can cause problems with civilisations around the universe that we are trying to have a better relationship with."
In response to the regulations, the European occupants of the International Space Station have begun photographing and fingerprinting all US astronauts arriving at the station.
The Green Party said although it is in no way affiliated with little green men from Mars, Martians were being unfairly discriminated against, and urged Washington to remove the planet from its list of security threats.
The European Space Agency is still searching for the missing British-built Beagle 2 and has denied that it has any knowledge of similar measures being prepared at EU borders.